GPT GrassValley hydrogeological investigation report ...

Compiled by:

Geo Pollution Technologies – Gauteng (Pty) Ltd

81 Rauch Street

Georgeville

Pretoria

0184

P.O. Box 38384

Garsfontein East

0060

Tel: +27 (0)12 804 8120

Fax: +27 (0)12 804 8140

HYDROGEOLOGICAL REPORT

FOR

PROPOSED VOLSPRUIT MINE (NORTH PIT)

NEAR MOKOPANE

GPT Reference Number: EaGrn-10-115

Version: Final Version 1

Date: July 2010

Compiled for:

EScience Associates (Pty) Ltd

HYDROGEOLOGICAL REPORT FOR THE PROPOSED VOLSPRUIT MINE (NORTH PIT)

GEO POLLUTION TECHNOLOGIES – GAUTENG (PTY) LTD i

Report Type: Hydrogeological Report

Project Title: Hydrogeological Report for the Proposed Volspruit Mine (North Pit) near Mokopane

Site Location: On the farm Volspruit 326KP, Mokopane

Limpopo Province

Compiled For: EScience Associates (Pty) Ltd

Compiled By: A. Freysen (B.Sc., Hons) (Chapter 3, 5.5, 5.6, 5.7)

K.H. Vermaak (M.Sc.) (Chapter 4, 5.1, 5.2, 5.3, 5.4)

B. J. Bredenkamp (M.Sc., Pr.Sci.Nat) (Chapter 6, 7, 8, 11, report editing)

G.J. du Toit; (D.Sc., Pr.Sci.Nat) (Chapter 9, 10, quality control)

GPT Reference: EaGrn-10-115

Version: Final Version 1.0

Date: July 2010

Distribution List: PDF to EScience Associates

(Current Version)

Disclaimer:

The results and conclusions of this report are limited to the Scope of Work agreed between GPT and the Client for whom this investigation has been conducted. All assumptions made and all information contained within this report and its attachments depend on the accessibility to and reliability of relevant information, including maps, previous reports and word-of-mouth, from the Client and Contractors. All work conducted by GPT is done in accordance with the GPT Standard Operating Procedures. GPT is in the process of obtaining ISO 9001:2008 accreditation.

Copyright:

The copyright in all text and other matter (including the manner of presentation) is the exclusive property of Geo Pollution Technologies – Gauteng (Pty) Ltd, unless where referenced to external parties. It is a criminal offence to reproduce and/or use, without written consent, any matter, technical procedure and/or technique contained in this document. This document must be referenced if any information contained in it is used in any other document or presentation.

Declaration:

I hereby declare: 1. I have no vested interest (present or prospective) in the project that is the subject of this report as well as its

attachments. I have no personal interest with respect to the parties involved in this project. 2. I have no bias with regard to this project or towards the various stakeholders involved in this project. 3. I have not received, nor have I been offered, any significant form of inappropriate reward for compiling this

report.

B.J. Bredenkamp, M.Sc.,Pr.Sci.Nat Professional Natural Scientist (No 400015/09) Geo Pollution Technologies – Gauteng (Pty) Ltd

Quality Control: This report was checked by:

G.J. du Toit; D.Sc.,Pr.Sci.Nat Professional Natural Scientist (No 400043/86) Geo Pollution Technologies – Gauteng (Pty) Ltd

Customer Satisfaction: Feedback regarding the technical quality of this report (i.e. methodology used, results discussed and recommendations made), as well as other aspects, such as timeous completion of project and value of services rendered, can be posted onto GPT’s website at www.gptglobal.com.

http://www.gptglobal.com/


GEO POLLUTION TECHNOLOGIES – GAUTENG (PTY) LTD ii

TABLE OF CONTENTS

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

2 SCOPE OF WORK .......................................................................... 1

3 METHODOLOGY ........................................................................... 2

3.1 DESK STUDY ...................................................................................... 2

3.2 HYDROCENSUS ................................................................................... 2

3.3 SAMPLING AND CHEMICAL ANALYSIS .......................................................... 2

3.4 GEOPHYSICAL SURVEY .......................................................................... 3

3.4.1 Objectives of Geophysical Survey .......................................................... 3

3.4.2 Survey Methods and Instrumentation ...................................................... 3

3.5 BOREHOLE DRILLING ............................................................................ 3

3.6 PUMP TESTING ................................................................................... 3

3.6.1 Aquifer Parameters ........................................................................... 4

3.6.1.1 Aquifer Test Pro ....................................................................... 4

3.6.2 Groundwater Recharge Estimation ......................................................... 4

3.6.3 Numerical Groundwater Modelling ......................................................... 5

4 DESCRIPTION OF MINE ENVIRONMENT ................................................ 6

4.1 CLIMATE .......................................................................................... 6

4.2 TOPOGRAPHY AND DRAINAGE ................................................................. 6

4.3 REGIONAL GEOLOGY ............................................................................ 7

4.3.1 Site Geology ................................................................................... 7

4.4 REGIONAL HYDROGEOLOGY .................................................................... 9


GEO POLLUTION TECHNOLOGIES – GAUTENG (PTY) LTD iii

5 RESULTS OF INVESTIGATION .......................................................... 14

5.1 HYDROCENSUS .................................................................................. 14

5.2 GEOPHYSICAL SURVEY ......................................................................... 18

5.3 BOREHOLE DRILLING ........................................................................... 20

5.4 PUMP TEST ANALYSIS .......................................................................... 21

5.4.1 Aquifer Parameters .......................................................................... 22

5.4.2 Groundwater Recharge Estimation ........................................................ 24

5.5 WATER LEVELS .................................................................................. 25

5.6 POTENTIAL CONTAMINANTS................................................................... 26

5.6.1 Acid generation capacity of the rock ..................................................... 27

5.6.2 Leach test..................................................................................... 28

5.6.3 Acid rock drainage (ARD) formation ...................................................... 30

5.7 WATER QUALITY ................................................................................ 30

5.7.1 Quality control ............................................................................... 30

5.7.2 Water quality discussion .................................................................... 31

5.7.3 Discussion of groundwater chemistry and health risks ................................. 38

6 GROUNDWATER VULNERABILITY ..................................................... 39

7 AQUIFER CLASSIFICATION ............................................................. 40

7.1 AQUIFER PROTECTION CLASSIFICATION ..................................................... 41

8 SITE CONCEPTUAL MODEL ............................................................ 43

8.1 IMPACT SOURCE ................................................................................ 43

8.1.1 Opencast mine ............................................................................... 43

8.1.2 Waste rock dumps ........................................................................... 46


GEO POLLUTION TECHNOLOGIES – GAUTENG (PTY) LTD iv

8.1.3 Tailings dams ................................................................................. 46

8.1.4 Workshops, septic tanks and domestic waste disposal sites........................... 46

8.2 PATHWAYS ...................................................................................... 47

8.2.1 Site specific hydrogeology .................................................................. 47

8.3 RECEPTORS ...................................................................................... 48

9 NUMERICAL MODEL ..................................................................... 50

9.1 FLOW MODEL CONSTRUCTION ................................................................ 50

9.1.1 Elevation data ................................................................................ 50

9.1.2 Lateral Boundaries .......................................................................... 54

9.1.3 Vertical Delineation ......................................................................... 54

9.2 FIXED AQUIFER PARAMETERS ................................................................. 56

9.3 MODEL RUNS .................................................................................... 62

9.4 LIMITATIONS OF THE MODELLING EXERCISE: ............................................... 62

10 HYDROGEOLOGICAL IMPACTS AND PUMPING REQUIREMENTS ................ 63

10.1 OPERATIONAL PHASE ........................................................................ 63

10.1.1 The entire northern pit................................................................... 63

10.1.2 North-eastern shallower pit ............................................................. 68

10.1.3 Potential mitigations (GROUNDWATER QUANTITY) ................................... 73

10.1.3.1 Hydraulically isolation of the entire pit........................................... 73

10.1.3.2 Other potential mitigation measures .............................................. 73

10.2 POST MINING PHASE ......................................................................... 74

10.2.1 Groundwater Quantity .................................................................... 74

10.2.2 Groundwater Quality (opencast related) .............................................. 74


GEO POLLUTION TECHNOLOGIES – GAUTENG (PTY) LTD v

10.2.3 Groundwater Management ............................................................... 85

11 CONCLUSIONS AND RECOMMENDATIONS ......................................... 87

APPENDIX A: HYDROCENSUS DATA ....................................................... 90

APPENDIX B: GEOPHYSICAL REPORT ..................................................... 91

APPENDIX C: BOREHOLE LOGS ............................................................ 92

APPENDIX D: AQUIFER TEST RESULTS (AQUIFER PARAMETERS) .................... 93

APPENDIX E: LABORATORY CERTIFICATE OF ANALYSES ............................. 94


GEO POLLUTION TECHNOLOGIES – GAUTENG (PTY) LTD vi

LIST OF FIGURES

FIGURE 1: CORE RECOVERY AND RQD VARIATION WITH DEPTH .............................................. 9

FIGURE 2: TOPOGRAPHICAL MAP ................................................................................. 11

FIGURE 3: GEOLOGY MAP .......................................................................................... 12

FIGURE 4: BOREHOLE POSITIONS ON VOLSPRUIT 326 KP (PORTION 1) ..................................... 13

FIGURE 5: ESTIMATED YIELD OF BOREHOLES ................................................................... 17

FIGURE 6: GEOPHYSICAL TRAVERSES ............................................................................. 19

FIGURE 7: DRILL CHIPS FROM VOLSPRUIT PERCUSSION HOLE (VOL20) ..................................... 21

FIGURE 8: CORRELATION GRAPH INCLUDING ALL BOREHOLES ............................................... 26

FIGURE 9: PIE DIAGRAMS OF GROUNDWATER AND SURFACE WATER CHEMISTRY ......................... 35

FIGURE 10: STIFF DIAGRAMS OF GROUNDWATER AND SURFACE WATER CHEMISTRY .................... 36

FIGURE 11: PIPER DIAGRAM ........................................................................................ 37

FIGURE 12: CONCEPTUAL GROUNDWATER DRAWDOWN AND FLOW MODEL ............................... 45

FIGURE 13: SRTM ELEVATION POINTS ............................................................................ 52

FIGURE 14: SRTM ELEVATION DATA .............................................................................. 53

FIGURE 15: BOUNDARIES OF THE NUMERICAL MODEL ......................................................... 59

FIGURE 16: LATERAL DELINEATION OF THE MODELLED AREA ................................................ 60

FIGURE 17: LATERAL DELINEATION IN THE MINING AREA ..................................................... 61

FIGURE 18: PREDICTED GROUNDWATER DRAWDOWN IN YEAR 5 ............................................ 64

FIGURE 19: PREDICTED GROUNDWATER DRAWDOWN IN YEAR 10 ........................................... 65


FIGURE 21: PREDICTED GROUNDWATER LEVELS IN YEAR 15 ................................................. 67



FIGURE 24: PREDICTED GROUNDWATER LEVELS IN YEAR 5 ................................................... 72

FIGURE 25: CROSS SECTION OF HYDRAULIC BARRIERS BEFORE MINING .................................... 76

FIGURE 26: CROSS SECTION OF HYDRAULIC BARRIERS AT END OF MINING ................................ 77




FIGURE 30: PLUME MIGRATION FULL NORTHERN OPENCAST AFTER 10 YEARS ............................ 81



FIGURE 33: PLUME MIGRATION NORTH-EASTERN SECTION AFTER 80 YEARS .............................. 84


GEO POLLUTION TECHNOLOGIES – GAUTENG (PTY) LTD vii

LIST OF TABLES

TABLE 1: S-PAN EVAPORATION DATA (DOORNDRAAI DAM) .................................................... 6

TABLE 2: HYDROCENSUS SUMMARY ............................................................................... 15

TABLE 3: SUMMARY OF BOREHOLE DRILLING ................................................................... 20

TABLE 4: PUMP TEST INFORMATION .............................................................................. 23

TABLE 5: SUMMARY OF DATA GAINED FROM PUMP TESTS PERFORMED AT VOLSPRUIT .................. 23

TABLE 6: SUMMARY OF RECHARGE INCLUDING THE CL METHOD ............................................ 25

TABLE 7: SAMPLING DEPTHS FOR ABA............................................................................ 27

TABLE 8: RESULTS OF ACID BASE ACCOUNTING ................................................................ 27

TABLE 9: MATERIAL TYPE CLASSIFICATION ...................................................................... 27

TABLE 10: ANALYTICAL RESULTS OF DISTILLED WATER LEACH TEST OF THE CORE SAMPLES .......... 29

TABLE 11: ANALYSIS RESULTS OF DUPLICATE SAMPLES ....................................................... 31

TABLE 12: RESULTS OF MAJOR CATION AND ANION ANALYSES .............................................. 33

TABLE 13: RESULTS OF MAJOR CATION AND ANION ANALYSES (CONTINUED) ............................. 34

TABLE 14: SUMMARY OF THE HUMAN HEALTH RISKS POSED BY THE RELEVANT CONSTITUENTS ....... 38

TABLE 15: RATINGS FOR THE GROUNDWATER QUALITY MANAGEMENT CLASSIFICATION SYSTEM...... 41

TABLE 16: GQM INDEX FOR THE STUDY AREA ................................................................... 41

TABLE 17: POTENTIAL RECEPTORS ............................................................................... 49

TABLE 18: CALCULATED AQUIFER PARAMETERS ................................................................ 58

TABLE 19: ALLOCATED AQUIFER PARAMETERS ................................................................. 58

TABLE 20: PREDICTED VOLUMES OF WATER TO BE PUMPED (ENTIRE PIT) ................................. 68

TABLE 21: PREDICTED VOLUMES OF WATER TO BE PUMPED (NORTH EASTERN SHALLOWER PIT) ..... 69


GEO POLLUTION TECHNOLOGIES – GAUTENG (PTY) LTD viii

LIST OF ABBREVIATIONS

HCO3 = Bicarbonate NO3 = Nitrate Cl = Chloride SO4 = Sulphate F = Fluoride Na = Sodium K = Potassium Ca = Calcium Mg = Magnesium Fe = Iron Mn = Manganese As = Arsenic Al = Aluminium Zn = Zinc B = Boron Ni = Nickel Co = Cobalt Cd = Cadmium Si = Silica Se = Selenium Cu = Copper Pb = Lead Ag = Silver TDS = Total Dissolved Solids EC = Electrical Conductivity Cat/an bal% = Cation/anion balancing error SSL = Soil screening level SWL = Static Water Level BDL = Below detection limit AH = Auger hole BH = Borehole DRO = Diesel Range Organics GRO = Gasoline Range Organics ICP-OES = Inductively Coupled Plasma Optical Emission Spectroscopy GC-MS = Gas Chromatography Mass Spectrometer GPT = Geo Pollution Technologies GW = Groundwater ℓ = litre m = metres mamsl = metres above mean sea level mbgl = metres below ground level mg/l = milligram per litre n.a. = not analysed ppm = parts per million


GEO POLLUTION TECHNOLOGIES – GAUTENG (PTY) LTD 1

1 INTRODUCTION

Geo Pollution Technologies (Pty.) Ltd. (GPT) was appointed by EScience Associates (Pty) Ltd to

conduct a hydrogeological study for the proposed Volspruit Mine (North Pit) located approximately

15km south of Mokopane on the farm Volspruit 326 KP, Limpopo Province. This report is not

intended to be a comprehensive description of the proposed project, but rather as a specialist

geohydrological study to evaluate the overall geohydrological character of the site.

2 SCOPE OF WORK

The following work program was envisaged in order to adhere to the scope of work:

A desk study was conducted, i.e. gathering of existing information from topographical

maps, ortho-photos, geological maps, hydrological information, meteorological information,

discussions with relevant mine personnel, studying of previous groundwater investigation

reports etc.

A borehole/spring census was done in the area (2 km around the proposed mining area) to

identify and update groundwater occurrence and utilisation in the area. Certain spot checks

were done on a 2-3km radius to determine the status of boreholes further away from the

mine, due to the proposed pit depths. The data gathered during this phase was used to

develop a groundwater-monitoring program.

The groundwater potential (quality & quantity) of the area was evaluated, based on the

information gathered during the hydrocensus. The data gathered during this phase assisted

in the development of a groundwater potential estimation as well as a groundwater-

monitoring program.

Sampling of the groundwater in the immediate vicinity of the proposed mine was conducted

to determine the current quality. The water samples was sent to an accredited laboratory.

Geochemical analyses were done to determine most likely leaching concentrations,

including acid base accounting (ABA).

A geophysical survey was done around the proposed pit areas to determine preferred

groundwater flow structures (faults and fractures). A resistivity survey and Stratagem

soundings (magneto telluric method) were conducted over the area.

Five boreholes were drilled in carefully selected positions which coincide with the

geophysical anomalies. The boreholes are suitable as monitoring boreholes.

Five boreholes were pump tested to determine the sustainable yield and aquifer

parameters of the boreholes. These pump tests entail a 24 hour constant discharge (CD)

test and 12 hour recovery. A 3 hour step discharge test preceded the constant test to

determine the optimum pump rate for the CD test.

Flow and transport modelling of the groundwater was performed to predict the long term

impacts on the receiving groundwater environment. The impacts associated with mining



activities can normally be subdivided into two aspects, namely the de-watering of the

surrounding aquifer during mining and the deterioration of the water quality in the

receiving aquifer system after mining. Both these aspects were addressed.

Inflow of groundwater into the mining areas was calculated from the groundwater model.

Data were interpreted for the prediction of the possible environmental impacts as well as

for the designing of mitigation measures where needed.

Recommendation of a groundwater monitoring network and comments on groundwater

monitoring and management.

3 METHODOLOGY

3.1 DESK STUDY

A complete desk study was conducted, entailing the gathering of information from the relevant

topographical maps (1:50 000-scale 2428BD Topographic Sheet), geological map (1:250 000 sheet

2428 Nylstroom) and Geohydrological map (Groundwater Resources of South Africa Sheets 1 and 2).

Data was obtained from the National Groundwater Database (NGBD) obtained from the Department

of Water Affairs (DWA). A number of internal reports obtained from the client were also used for

the compilation of the report.

3.2 HYDROCENSUS

A detailed hydrocensus was conducted on and around the site to an approximate distance of about

three kilometres so as obtain a representative population of the boreholes in the area. During the

hydrocensus, all available details of boreholes and borehole-owners were collected and included in

the hydrocensus forms. Water samples were collected from boreholes as described in the relevant

paragraph below. Information was collected on the use of the boreholes in the area, the water

levels and yields of boreholes, etc. The information can be used to assess the risk which potential

groundwater pollution poses to groundwater users.

3.3 SAMPLING AND CHEMICAL ANALYSIS

Groundwater was sampled according to the GPT Standard Operating Procedure for groundwater

samples by pumping and bailing where possible1. In summary, the procedure is to measure the

groundwater level before introducing any equipment in the borehole. Pump samples were collected

from boreholes with restricted access by pumping the hole for a period to ensure that a

representative sample of the aquifer is obtained. The groundwater samples were contained in pre-

1 Available on request from [email protected]

mailto:[email protected]



cleaned one litre plastic bottles. All samples were kept on ice or in a refrigerator until delivered to

a laboratory.

A total of 50 boreholes were identified during the hydrocensus on 11 & 12 May 2010. Five additional

boreholes were also drilled and water samples were collected from these boreholes as well. In

total, 18 groundwater samples and one surface water sample from the Nyl River samples were

collected. The water samples were sent to Clean Stream Scientific Services (Pty) Ltd in Pretoria for

major ion analysis to determine water quality in the area.

3.4 GEOPHYSICAL SURVEY

A geophysical was carried out during May 2010. The survey consisted of four traverses of CSAMT

(Controlled Source Array Magneto Telluric), and five traverses of direct current resistivity profiling.

3.4.1 Objectives of Geophysical Survey

The objective of this geophysical survey was to image the subsurface resistivity / conductivity in

order to investigate the geological structure of the area.

3.4.2 Survey Methods and Instrumentation

For this survey, the Geometrics “Stratagem” EH 4 CSAMT instrument and the ABEM “Lund”

resistivity imaging system were used. Both systems measure bulk resistivity from the surface as

apparent resistivity (Rho) vs. frequency (CSAMT) and apparent resistivity vs. a geometric factor (dc

resistivity). This is then converted to true resistivity vs. depth during the interpretation process.

The details pertaining to the methodology and instrumentation can be seen in Appendix B.

3.5 BOREHOLE DRILLING

Makulu Manzi drilling contractors were commissioned to drill five monitoring wells at the project

site. The holes were drilled using the rotary percussion drilling method. Four of the boreholes were

drilled on targets identified during the geophysics (VOL17, VOL18, VOL19 VOL20). One borehole

(VOL21) was drilled in the centre of the ore body to a depth of 170 meters below ground level to be

representative of the ore body. The depth of mining is likely to approach 160m.

3.6 PUMP TESTING

GPT appointed Trans Africa Water Services to conduct pump test on the newly drilled water supply

boreholes viz. VOL17, VOL19, VOL20, VOL21 and VOL22. VOL18 was used as an observation hole for

VOL22. The tests were conducted from 1 of June 2010 to the 17 of June 2010. The pump tests were

conducted according to the SANS 10299-4 standard. A step discharge test was initially conducted on

each borehole to determine the rate at which it should be pump during the constant discharge test.

The constant discharge test was conducted for a 24 hour period followed by a 12 hour recovery to

determine the aquifer hydraulic properties (transmissivity and storativity). It was also necessary to



identify any boundaries, which may have an effect on the long term sustainable yield of the

borehole. Observation boreholes were monitored where available.

3.6.1 Aquifer Parameters

The aquifer parameters were determined from the pump tests. The transmissivity and storativity

was estimated by curve fitting in Aquifer Test Pro2 and by calculation in FC-Method3.

Transmissivity is the rate at which water is transmitted through a unit width of an aquifer under a

unit hydraulic gradient, while storativity is the volume of water per volume of aquifer released as a

result of a change in head. Steady-state can be defined as the situation where variations of the

drawdown with time are negligible, or where the hydraulic gradient has become constant.4

3.6.1.1 Aquifer Test Pro

Curve fitting of the aquifer data was used to determine the transmissivity and storativity. The

double porosity (uniformly fractured aquifers) method by Warren and Root (1963)2 presented the

best fit. This method stipulates flow from the blocks (porous medium) to the fractures. The

fractured rock mass is assumed to consist of two interacting and overlapping continua: a continuum

of low-permeability primary porosity blocks, and a continuum of high permeability, secondary

porosity fissures or fractures.

The assumptions and conditions underlying this method are:

The aquifer is isotropic and confined

The thickness of the aquifer is uniform over the area of influence.

The extent of the aquifer is infinite (no barriers causing preferential flow paths),

Constant discharge rate were used in the pump testing

The well fully penetrates a fracture (matrix and fracture is considered as two overlapping

continuous media),

Horizontal piesometric surfaces exist prior to pumping

Pseudo steady state conditions is achieved

3.6.2 Groundwater Recharge Estimation

The groundwater recharge was estimated using the RECHARGE program5, which includes using

qualified guesses as guided by various schematic maps. The following methods/sources were used

to estimate the recharge.

Soil information

2 Aquifer Test Pro version 4.0, developed by Waterloo Hydrogeologic Inc

3 Flow Characteristic method version 2.0 developed by the University of the Free State

4 Kruseman, G.P. and de Ridder N.A. (1991), Analysis and Evaluation of Pumping Test Data, 2nd ed., ILRI publication 47,The Netherlands 5 Gerrit van Tonder, Yongxin Xu: RECHARGE program to Estimate Groundwater Recharge, June 2000. Institute for Groundwater Studies, Bloemfontein RSA.

mk:@MSITStore:C:/Users/bbredenkamp/Documents/MSc/Groundwater_Dictionary.chm::/Introduction/Aquifer.htm

mk:@MSITStore:C:/Users/bbredenkamp/Documents/MSc/Groundwater_Dictionary.chm::/Introduction/Hydraulic_Gradient.htm



Geology

Groundwater Recharge Map (Vegter)

Acru Recharge Map (Schulze)

Harvest Potential Map

Chloride (Cl) method

The above-mentioned programme incorporates all the different methods to calculate recharge. The

following assumptions are necessary for successful application of the Cl Method:

There is no source of chloride in the soil water or groundwater other than that from

precipitation

Chloride is conservative in the system

Steady-state conditions are maintained with respect to long-term precipitation and chloride

concentration in that precipitation, and in the case of the unsaturated zone

A piston flow regime, which is defined as downward vertical diffuse flow of soil moisture, is

assumed.

3.6.3 Numerical Groundwater Modelling

The finite difference numerical model was created using the US Department of Defence

Groundwater Modelling System (GMS7) as Graphical User Interface (GUI) for the well-established

Modflow and MT3DMS numerical codes.

MODFLOW is a 3D, cell-centred, finite difference, saturated flow model developed by the United

States Geological Survey. MODFLOW can perform both steady state and transient analyses and has

a wide variety of boundary conditions and input options. It was developed by McDonald and

Harbaugh of the US Geological Survey in 1984 and underwent several overall updates since. The

latest update (Modflow 2000) incorporates several improvements extending its capabilities

considerably, the most important being the introduction of the new package called the Layer-

Property Flow Package.

MT3DMS is a 3-D model for the simulation of advection, dispersion, and chemical reactions of

dissolved constituents in groundwater systems. MT3DMS uses a modular structure similar to the

structure utilized by MODFLOW, and is used in conjunction with MODFLOW in a two-step flow and

transport simulation. Heads are computed by MODFLOW during the flow simulation and utilized by

MT3DMS as the flow field for the transport portion of the simulation.



4 DESCRIPTION OF MINE ENVIRONMENT

The Volspruit Project is located 15 kilometres south of the town of Mokopane (previously

Potgietersrus) in the Limpopo Province of South Africa. The project area is located on the farm

Volspruit 326 KP (Portion 1).

4.1 CLIMATE

The proposed site is located in the summer rainfall region of Southern Africa with precipitation

usually occurring in the form of convectional thunderstorms. The area experiences warm to hot

summers with an average maximum temperature of 26° and an average minimum of 17°. Winters

are mild with an average maximum of 17°C and an average minimum of 8°C. Rainfall is during the

summer months and averages 95mm per month. The mean annual rainfall is 625mm per annum.6

The S-pan evaporation data from the Doorndraai Dam located ~18km north west of the proposed

mine estimated an average annual evaporation of 1770mm7 (Table 1).

Table 1: S-pan evaporation data (Doorndraai Dam)

Month S- pan Evaporation (mm)

October 192.1

November 184.9

December 193.5

January 193

February 163.8

March 156.3

April 122.8

May 101.7

June 80.9

July 88

August 122.7

September 161.8

Total 1770.1

4.2 TOPOGRAPHY AND DRAINAGE

The topography can normally be used as a good first approximation of the hydraulic gradient in an

aquifer. The site is located adjacent to the Nyl River which flows in a north-easterly direction

6 Groundwater Resource Directed Measures. V 2.5

7 S-pan evaporation data for Doorndraai Dam available from http://www.dwaf.gov.za/hydrology



towards the town of Mokopane. Locally the surface drains in a westerly direction, towards the

adjacent Nyl River. Regionally the drainage is in a north easterly direction. The area of interest

forms part of the A61E Quaternary catchment.

4.3 REGIONAL GEOLOGY

The Bushveld Complex consists of the eastern, western, northern and southern limbs as well as

satellite outcrops at Nietverdiend (far west) and Villa Nora (far north). According to dating of the

rocks, they fall partly into the Vaalian Erathem and partly in the Mokolian Erathem. The main

Bushveld Igneous Complex intruded into rocks of the Transvaal Supergroup, largely along an

unconformity between the Magaliesberg quartzite of the Pretoria Group and the overlying Rooiberg

felsites. The total extent of the Bushveld Complex is approximately 66,000km2, just over half of

which is covered by younger formations.8

The Volspruit Project is situated on the northern limb, where the mafic rocks have a different

sequence to those of the eastern and western limbs. Furthermore, the Bushveld rocks transgress

the Transvaal Supergroup from the Smelterskop and Magaliesberg formations in the south to the

ironstones of the Penge formation further north, the dolomites of the Malmani Subgroup and

eventually resting on the Archaean Turfloop granite in the extreme north.9

The mafic rocks of the Bushveld Complex host layers rich in PGE’s (Platinum Group Elements),

chromium and vanadium, and constitute the world's largest known resource of these metals. In

addition, nickel and copper are generally associated with the deposits and are significant by-

products. The mafic rocks of the eastern and western limbs (collectively termed the Rustenburg

Layered Suite) have been divided into five zones known as the Marginal, Lower, Critical, Main and

Upper Zones, from the base upwards.8

4.3.1 Site Geology

The rocks underlying the Volspruit Project comprise cumulates of the Lower Zone of the Rustenburg

Layered Suite of the Bushveld Complex and its immediate floor rocks consisting of the Transvaal

Supergroup. The succession is dominated by ultramafic cumulates which range in composition from

dunites and harzburgites to orthopyroxenites.8

The zone of PGE and base metal sulphide mineralisation which has been targeted by the Volspruit

exploration (informally referred to as the Volspruit PGE-Ni Reef) is hosted in pyroxenites

(orthopyroxenites cumulates) in the lower portion of the upper Volspruit sub-zone. This zone

usually occurs several tens of metres above an approximately 100m thick zone of harzburgites

8 IGS, June 2010, Geological And Resource Estimation Report On The Grass Valley Project, Volspruit

326KR,Limpopo Province, South Africa

9 IGS GV BFS Geology Report – June 2010 after Vermaak and Van der Merwe, 2000



(olivine cumulates), which is the only significant sequence of harzburgites in the Volspruit sub-

zone.8

The current distribution of the various Lower Zone units is controlled by several major episodes of

post and possibly syn-Bushveld faulting. Outcrop is extremely poor in the Volspruit area and

structure is best revealed by the aeromagnetic data acquired by IGS. Faulting most likely occurred

in three phases: an initial, block faulting episode (reverse-faulting) resulted in horsts of Lower Zone

being emplaced into the upper portions of the Rustenburg Layered Suite and into higher sediments.

The second generation of faulting, along a WNW-ESE trend, was also reverse faulting, resulting in a

stepped arrangement in the Rustenburg Layered Suite. The third phase of faulting along a south-

westerly trend resulted in the uplift of wedges of Transvaal sediments into the Rustenburg Layered

Suite.8

Contamination of the sequence by partly digested country rock xenoliths and by melts of floor rock

litho-types is more common in the footwall harzburgite than in the pyroxenitic sequence. Often a

coarse-grained to pegmatoidal feldspathic pyroxenite/norite is encountered that may contain

coarse nuggets of sulphide.8

The ore body has a fairly flat lying disposition: the ore zone is shallowest in the north-east, but

down-faulted to the south and west to a depth of approximately 70 to 90 metres at the south

western extent of the body. The eastern and southern margins of the body are fault-bounded;

exploration of the western edge is constrained by the floodplain of the Nyl River; the property

boundary defines the northern limit of the body.8

The borehole database provided by IGS10 was used to characterise the weathering. As a result, the

recovery percentage and RQD (rock quality designation), where available, was used to estimate

depth of weathering. Only the core holes drilled by IGS in 2010 were used, as the necessary

parameters were logged sufficiently. A polynomial trend was used to fit the data points as seen in

Figure 1. RQD was not logged in all the cores, however in the cores where RQD was logged a very

good correlation good be seen between RQD and recovery percentage. As can be seen in Figure 1,

the depth of weathering (and/or fracturing) is dominant in the first 50-60mbgl. This figure also

suggests that fractures or conduits are found deeper in the rock profile as well.

10 Integrated Geological Solutions (Pty) Ltd



Figure 1: Core recovery and RQD variation with depth

4.4 REGIONAL HYDROGEOLOGY

As previously mentioned, the rocks underlying the Volspruit Project comprise cumulates of the

Lower Zone of the Rustenburg Layered Suite of the Bushveld Complex and floor rocks consisting of

the Transvaal Supergroup. Groundwater in these rocks is usually associated with deeply weathered

and fractured mafic rocks11. The groundwater yield potential in the Eastern Limb of the Bushveld

Complex is regarded as low as 81% of the boreholes on record have a yield less than 2l/s.11

In the Northern Limb, the Rustenburg Layered Suite rocks are mainly found in the valleys and flat

areas with widespread groundwater resources12. Borehole yields of 0.5 – 2 l/s are common, with >5

l/s found in localised areas.12 Potgietersrus Platinum Mines (PPL) have a permit to abstract up to 1

500 m3/d from an abandoned chrome mine south of Mokopane in the catchment A61E (in which the

Volspruit project is found).12 Groundwater use in the A61E catchment is at the limit of the

11 An explanation of the 1:500 000 General Hydrogeological Map Johannesburg 2526, Barnard,

October 2000 – DWAF.

12 Department of Water Affairs and Forestry, South Africa. 2004. Internal Strategic Perspective:

Limpopo Water Management Area : Prepared by Goba Moahloli Keeve Steyn (Pty) Ltd, in association

with Tlou & Matji (Pty) Ltd and Golder Associates (Pty) Ltd. on behalf of the Directorate: National

Water Resource Planning. Report No. P WMA 01/000/00/0304.



estimated sustainable yield. A present status category of D, (80-100 % of recharge) is already

used13. Therefore the volume of allocatable groundwater for use in this catchment is limited.

In general, the Bushveld Complex is generally characterised by low permeability strata, with

transmissivity being dependant on the amount of fracturing. As a result abstraction boreholes in the

Bushveld setting usually have poor and unsustainable yields. However it is apparent that a larger

extent of faulting and fracturing is found in certain areas of the Northern Limb than in the rest of

the Bushveld Complex (as is the case at Volspruit). This occurrence is likely to increase borehole

yields and sustainability in these areas.14

The groundwater quality is generally classified as good, with isolated NO3 pollution present in the

settlements. Mining in the area has the potential to pollute and should be recognised.12

Groundwater contributes to surface water base flow throughout the catchment via sub surface

seepage and springs. The Waterberg and Soutpansberg Ranges are important areas for groundwater

recharge and drainage base flow. The relationship between groundwater, base flow, and river flow

is reasonably well understood where hydrographs are available. However, the impact of

groundwater abstraction on surface water resources is less well understood. Recharge of the

groundwater system from river flow, especially during flood events, is important13.

13 Department of Water Affairs and Forestry, South Africa. 2005. Groundwater Resource Assessment

Phase II Project 4 Methodology for Classification Final Report: Prepared by Goba Moahloli Keeve

Steyn (Pty) Ltd, in association with Tlou & Matji (Pty) Ltd and Golder Associates (Pty) Ltd. on behalf

of the Directorate: National Water Resource Planning. Report No. P WMA 01/000/00/0304.

14 GENMIN, 1990, Platinum Group Metals Section, The Hydrogeology of the Volspruit Project Area,

Bulletin no. 318



Figure 2: Topographical Map



Figure 3: Geology Map



Figure 4: Borehole Positions on Volspruit 326 KP (Portion 1)



5 RESULTS OF INVESTIGATION

5.1 HYDROCENSUS

A total of 50 hydrocensus boreholes and one surface water body (Nyl River) was located in a 2-3 km

radius around the project area. The results of the hydrocensus is summarised in Table 2 below. The

borehole positions are depicted in Figure 2 and Figure 4.

Of the 50 boreholes identified, it wasn’t possible to measure the water levels in 19 of the boreholes

as they were equipped with pumps thus preventing access. The water levels ranged from 1.5 to 38

mbgl, and averaged at 17.3 mbgl. Boreholes which were found inside the 2 km radius are inferred

to be relevant and may potentially be impacted on by the activities of the mine. Only 7 boreholes

identified around the proposed mine area are not in use.

Groundwater data was also obtained from the DWA National Groundwater Database (NGDB). No

clear correlation between the NGDB boreholes and the hydrocensus boreholes could be made. This

most likely due to a discrepancy in the DWA borehole coordinate data. Due to the discrepancy and

the relative age of the data, it was decided that this data would not be taken into consideration for

the study.

Groundwater is intensively used for pivot irrigation, potable water and livestock watering. Large

amounts of water are abstracted from the aquifer for irrigation purposes especially on the farms

Volspruit and Bokpoort. The large scale groundwater abstraction may stress the aquifer especially if

more groundwater is being abstracted than what is recharged to the aquifer. Details of the

hydrocensus can be seen in Appendix A.

The boreholes indentified during the hydrocensus around the proposed mine show an average yield

of 6.5 l/s. The yields experienced in the Volspruit area are significantly higher than expected for

that particular area. These higher yields can be attributed to deep weathering and fracturing, as

well as fault structures forming preferential flow paths. The newly drilled boreholes at the

proposed mine are also good yielding boreholes with borehole VOL20 having a yield of 8l/s. The

siting of strong yielding boreholes using scientific methods illustrates the efficiency of geophysical

techniques for this particular area. Figure 5 depicts classed posts of the yields of boreholes which

were determined during the hydrocensus and drilling.



Table 2: Hydrocensus Summary

Borhole Number

Coordinates Owner

Est. Yield (l/s)

When last pumped

Use SWL

(mbgl)

Collar Height (mm) Y X

ABDUL 24.34726 28.9371 Abdulla unknown more than 24 Irrigation 6.18 450

DEK1 24.37587 28.97 De Klerk unknown within24 Domestic 24.86 0

NYL1 24.31476 28.9507 - - - River - -

GV1 24.29885 28.9847 E. Wroe unknown within24 Domestic 31.15 200

GV2 24.29966 28.9816 E. Wroe unknown within24 Domestic 25.3 0

GV3 24.29395 28.9907 Not at home unknown within24 Domestic 29.8 350

GV4 24.29729 28.9913 Mandev unknown within24 Domestic 29.4 0

GV5 24.31797 28.9866 K. Kusbach unknown currently Domestic 28.8 315

GV6 24.32036 28.9707 Mine unknown within24 Domestic no access NA

GV7 24.31494 28.9621 Not at home unknown 24+ Irrigation 23.42 550

GV8 24.33496 28.9737 Niemcor unknown 24+ Irrigation 37.75 270

VOLS1 24.3678 28.9636 D. De Beer 9 within24 domestic and

Irrigation 27.85 0

VOLS2 24.36994 28.9646 D. De Beer 5 currently Irrigation no access NA

VOLS3 24.37002 28.9641 D. De Beer 4 currently Irrigation 23.81 0

VOLS4 24.3699 28.965 D. De Beer unknown never Not in use 24.3 0



VOLS7 24.37607 28.9546 D. De Beer unknown 24+ Irrigation no access 0

VOLS8 24.37545 28.9546 D. De Beer unknown 24+ Irrigation 9.98 0

VOLS9 24.3747 28.955 D. De Beer unknown 24+ Not in use 10.7 490

VOLS10 24.37377 28.9558 D. De Beer unknown 24+ Irrigation no access NA

VOLS11 24.37355 28.9603 D. De Beer 4 24+ Irrigation 15.17 0

VOL1 24.3463 28.9479 P.J. De Klerk unknown never Not in use (old

core holes) 6.42 500


core holes) 6.85 500


core holes) 7.6 600

VOL4 24.34185 28.9463 P.J. De Klerk 33 24+ Irrigation no access NA




VOL8 24.34806 28.9523 P.J. De Klerk unknown 24+ Irrigation no access NA



VOL11 24.34753 28.9558 P.J. De Klerk unknown 24+ Not in use 20.08 100

VOL12 24.34806 28.9571 P.J. De Klerk 3 24+ Irrigation no access 0

VOL13 24.35341 28.9561 P.J. De Klerk 3 within24 Domestic 24.19 350

VOL14 24.35528 28.9533 P.J. De Klerk 3 within24 Domestic no access NA



BOK1 24.37809 28.9726 J. De Klerk unknown within24 Domestic 7.53 0

BOK2 24.37719 28.9733 J. De Klerk unknown within24 Domestic no access 0



BOK3 24.37763 28.9723 J. De Klerk unknown within24 Domestic 11.88 0

BOK4 24.39179 28.9668 J. De Klerk unknown 24+ Not in use 15 0

BOK5 24.39167 28.9662 J. De Klerk unknown 24+ Irrigation 15.26 0



BOK8 24.39198 28.9659 J. De Klerk unknown 24+ Irrigation no access NA





VOL17 24.34225 28.9458 P.J. De Klerk 2 never Newly Drilled 8.38 150

VOL18 24.34219 28.9524 P.J. De Klerk 1 never Newly Drilled 19.5 NA


VOL22 24.3424 28.9524 P.J. De Klerk 15 never Not in use 13.53 0





Figure 5: Estimated yield of boreholes



5.2 GEOPHYSICAL SURVEY

The main purpose of the geophysical survey on the farm Volspruit 326 KP was to identify areas

where possible preferential flow paths could be located on which boreholes may be targeted. The

positions of the traverses can be seen in Figure 6. The following observations were made:

Traverse 1 is located on the western limit of the survey area and was surveyed from south to north

for a total distance of 1200m to investigate the inferred fault at approximately 850m along the

traverse, and to test for possible structures along the river towards the south. Borehole VOL17 was

drilled on this anomaly. The AMT data indicate the presence of a sub-horizontal conductive zone

below the resistive basement signature of the DC (direct current) resistivity image and two sub-

vertical conductive zones. The northern sub-vertical conductor coincides well with the expected

fault position. An anomaly inferred to be deep weathering was identified at 230m, borehole VOL20

was drilled on this anomaly.

Traverse 2 was surveyed from SE to NW for 800m to intersect a range of inferred fault systems. The

AMT data is insensitive to the near surface but indicates a vertical conductor to the south of the

traverse. The expected fault zone(s) approximately 400m along the traverse are not clearly

discernable on either of the resistivity images although there is some indication of vertical

fracturing along the profile. The borehole VOL18 was drilled on the expected fault zone on 430m.

The existing borehole VOL22 is also found on this fault system.

Traverse 3 was surveyed roughly from south to north for a total distance of 700m. The expected

fault zone at approximately 100m along the traverse appears to manifest as a weak sub-vertical

conductive anomaly in both the resistive and less resistive horizons.

Traverse 4 was surveyed in the same direction as traverse 3 for a total distance of 500m. The AMT

resistivity image is not clear and appears to be influenced by power line noise. There is however an

indication of a sub vertical conductive anomaly at depth on the expected fault position 300m along

the traverse. Borehole VOL19 was drilled at 280m on this anomaly.

Traverse 5 was surveyed for a distance of 1200 m with the DC resistivity method only as the power

line interference along this traverse saturated the AMT magnetic coils. The data does not however

have the depth penetration / resolution to identify any of the fault systems with a deeper signature

in this area. The geophysical images can be seen in the geophysical report attached Appendix B.



Figure 6: Geophysical Traverses



5.3 BOREHOLE DRILLING

Five boreholes were drilled by means of percussion drilling at the project site on Volspruit. The

boreholes were drilled on identified geophysical anomalies to depth of between 40 meters and 170

meters.

Four boreholes (VOL17, VOL18, VOL19, and VOL20) were drilled on identified geophysical anomalies,

while VOL21 was drilled in the deepest section of the proposed pit. The position of these boreholes

can be seen in Figure 4. The boreholes were drilled in order to perform pump tests to gain further

knowledge and understanding of the hydraulic parameters of the aquifer. The boreholes were

equipped with between 8 and 11 meters of solid 6” casing. A summary of the borehole drilling can

be seen below in Table 3. The borehole logs can be seen in Appendix C.

Table 3: Summary of borehole drilling

Borehole no.

Drilling Target Depth (mbgl)

Blow yield (l/s)

Solid Casing

(m)

Perforated Casing (m)

First Water strike (mbgl)

Purpose

VOL17 Fault 80 1.6 10 - 12 Monitor, Pump

Test

VOL18 Fault 40 0.5 8 - 25 Monitor, Pump

Test

VOL19 Fault 70 3 10 - 20 Monitor, Pump

Test

VOL20 Weathering

Zone 70 ~3 10 - 5

Monitor, Pump Test

VOL21 Centre of Pit 170 2 11 - 13 Monitor, Pump

Test

The geological logs from the newly drilled boreholes conformed to adjacent core holes’ logs, thus

substantiating the geological situation. The depth of weathered rock varied between 20 and 45

meters. First water strikes varied between 5 and 25 meters. In all cases the blow yield did not

increase with depth, this is indicative of most of the water bearing structures being within the upper

weathered zone, although some chips displayed fractured surfaces as deep as 35 meters.

Chip samples were taken at one meter intervals and logged accordingly. A photo of the percussion

chips can be seen Figure 7.



Figure 7: Drill chips from Volspruit percussion hole (VOL20)

5.4 PUMP TEST ANALYSIS

The pump tests were conducted to determine the aquifer parameters which can be used to estimate

the potential impact that the groundwater could have on the future pit and visa versa. The

parameters were also used in the construction of the numerical model.

The pump tests were conducted with a mono-pump (positive displacement). A summary of the pump

tests can be seen in Table 4. Observation borehole VOL18 is located 23.94 meters away from VOL22

and showed some response to the pumping in VOL22. While VOL21 was being pumped VOL1 (150m

away), VOL2 (200m away) and VOL3 (170m away) were used as observation wells; these wells showed

no drawdown. The remaining pump tested boreholes did not have any observation wells. A 24 hour

constant discharge test followed by a 12 hour recovery was conducted on each of the holes. These 24

hour constant discharge tests were preceded by a 4 hour step discharge test. All the tested

boreholes recovered to their static water level far within 12 hours. The pump tests are appended in

Appendix D.

The following observations can be made from the pump test diagnostic plots:

In VOL17, some affects of well bore storage can be seen at early times, while linear flow can

be seen shortly at early intermediate time. Fracture flow is seen at late intermediate time.

Bilinear flow is apparent at late times where one possible no-flow boundaries is encountered.



VOL19 shows the usual influence of well bore storage at early stages. Bi-linear flow occurred

from moderately early times to the end of the test.

VOL20: Well bore storage at early times. Bi-linear flow occurred from moderately early times

to the end of the test.

VOL21 shows the characteristic well bore storage at early times. The log-log plot flattens

indicating that a boundary has been reached, which in turn indicates that the fracture has

been reached and fracture flow is occurring. A closed no-flow boundary is reached at late

time.

VOL22 was initially pumped at 6 l/s, however a sufficient drawdown was not achieved after

24 hours. It was therefore decided to perform another test at 10 l/s. When pumped at this

higher rate well bore storage can be seen at early times, followed by linear flow and bilinear

flow.

5.4.1 Aquifer Parameters

The aquifer parameters were determined by means of calculation in FC3 and by curve fitting in

Aquifer Test Pro2. The estimated transmissivities (T) of the pump tested boreholes is summarised in

Table 5, while the curve fitted graphs can be seen in Appendix D. The transmissivities estimated in

FC3 and by curve fitting in Aquifer Test Pro2 are similar and mostly in the same order of magnitude.

The storativity (S) or specific storage (Ss) of aquifer can only accurately be estimated from an

observation borehole. Therefore the storativity or specific storage could only be estimated in VOL18

(an observation hole to VOL22).



Table 4: Pump Test Information

Borehole

Static water level

(mbgl)

Pump inlet

(mbgl)

Borehole Depth (mbgl)

Available drawdown

(m)

Drawdown (m)

Constant discharge rate (l/s)

Max drawdown achieved

(%)

100% recovery

(min)

VOL17 8.23 63.50 79.80 55.27 22.95 1.82 41.52 300.00

VOL19 14.96 63.50 70.20 48.54 10.42 6.53 21.47 1200.00

VOL20 1.10 51.50 68.70 50.40 13.41 6.05 26.61 840.00

VOL21 7.57 123.50 170.00 115.93 121.36 3.00 100.00 1080.00

VOL22(6l/s) 18.53 63.50 96.20 44.97 6.67 6.06 14.83 1080.00

VOL22(10l/s)

18.33 45.50 96.00 27.17 12.22 10.08 44.98 960.00

Table 5: Summary of data gained from pump tests performed at Volspruit

Borehole

Method

Basic FC3 Advanced FC3 Cooper-Jacob3

Recovery: t' vs. rise of water Level3

Aquifer Test2

Early T (m2/d)

Late T (m2/d)

Early T (m2/d)

Late T (m2/d)

Early T (m2/d)

Late T (m2/d)

Recovery T (m2/d)

Double Porosity

T (m2/d)

Observation Well

(VOL18)

Specific Storage (VOL18)

VOL17 5.14 1.75 5.14 1.75 - 4.04 4 4.58 -

VOL19 44.37 28.59 44.37 28.59 - 29.96 53 42 -

VOL20 32.56 24.75 32.56 24.75 - 29.96 48 22.8* -

VOL21 8.05 0.22 8.05 0.22 - 1.14 1.4 9.92 -

VOL22 (6 l/s) 81.25 51.63 81.25 51.63 - 58.34 115 14.5 67.8 5.53E-02

VOL22 (10 l/s) 51.02 42.27 51.02 42.27 - 96.85 57 23 158 1.06E-01

*No fit could be achieved for this borehole. The T value in the table was derived from recovery data in Aquifer Test Pro



5.4.2 Groundwater Recharge Estimation

The groundwater recharge was estimated using the RECHARGE program15 (van Tonder, et al., 2000),

which includes using qualified guesses as guided by various schematic maps. The following

methods/sources were used to estimate the recharge.

Soil information

Geology

Groundwater Recharge Map (Vegter)

Acru Recharge Map (Schulze)

Harvest Potential Map

Chloride (Cl) method

The above-mentioned programme incorporates all the different methods to calculate recharge. The

following assumptions are necessary for successful application of the Cl Method:

There is no source of chloride in the soil water or groundwater other than that from

precipitation.

Chloride is conservative in the system.

Steady-state conditions are maintained with respect to long-term precipitation and

constant chloride concentration in the precipitation and the unsaturated zone.

A piston flow regime is assumed, defined as the downward vertical diffuse flow of soil

moisture.

According to the rainfall data, the average rainfall of the A61E catchment is 625 mm/year. The

A61E catchment has a total area of 547.2 km2. A Cl concentration of ~40.9 mg/ℓ was used in the Cl

method estimation. The concentration was calculated as the harmonic mean of the Cl

concentrations in the sampled boreholes unlikely to be affected by any contaminants. The other

methods used to estimate the recharge are qualified guesses derived from certain thematic maps

and equations15.

The result of the estimations including the Cl method can be seen in Table 6. It can be seen that

the groundwater recharge is averaged at 3.5% percent of the rainfall.

It is evident that the Cl method estimates a slightly lower recharge (3.2%) than the qualified

guesses. However, the recharge calculated with the Cl method is similar to that found by Vegter,

Acru and the harvest potential. Therefore a recharge of 3.2% was deemed to be the most realistic

value for this area. The average volume of groundwater recharge over the A61E catchment is

therefore calculated at 11.993 Mm3/annum.

15 Van Tonder, G.; Xu, Y. 2000. RECHARGE program to Estimate Groundwater Recharge. Bloemfontein: Institute for Groundwater Studies, 2000.



Table 6: Summary of Recharge Including the Cl Method

Method mm/a % of rainfall Certainty (Very High=5 ; Low=1)

Cl 20 3.2 4

Qualified Guesses :

Soil 56.3 9.0 3

Geology 31.9 5.1 3

Vegter 20.0 3.2 3

Acru 10.0 1.6 3

Harvest Potential 15.0 2.4 3

Base Flow (minimum Re) 7.0 1.1 1

Average recharge 21.9 3.5

5.5 WATER LEVELS

Water levels were measured in most (60%) of the boreholes during a hydrocensus conducted radius

on and around the project area during May 2010. Boreholes equipped with pumps prevented access

to measure water levels in some boreholes. The water levels ranged from 1.5 to 38 mbgl, and

averaged at 17.3 mbgl.

A good correlation is usually found between topography and static groundwater level. This

relationship can be used to distinguish between boreholes with water levels at rest, and boreholes

with anomalous groundwater levels due to disturbances such as pumping or local geohydrological

heterogeneities.

The static water level/topography relationship of the borehole data from the hydrocensus is shown

in Figure 8. It can be seen in the figure that a poor fit was obtained for most of the boreholes.

Therefore it appears that the groundwater level does not emulate the topography, especially on

the farm Volspruit. This can be expected as the aquifer is highly fractured (transmissive) and is

extensively used for irrigation. Static water levels plotting above the trend line were measured in

boreholes being pumped on a regular basis. The newly drilled boreholes and boreholes identified

during the hydrocensus viz. VOLS4, VOL1, VOL2, VOL3, VOL17, VOL18, VOL19, VOL20, VOL21,

VOL22 have never been pumped and are currently not in use. The water levels at the western part

of Volspruit Portion 1 near the river are shallower than the water levels further away. The

groundwater flow direction appeared to be toward the east (away from the Nyl river) at the time of

the investigation.

The groundwater study conducted by Genmin in 199014 also found the groundwater table as quite

flat (no significant gradient). The highly transmissive subsurface and over-abstraction of

groundwater is likely to result in the flat water table.



y = 1.1828x - 176.43R² = 0.60241050

1070

1090

1110

1050 1070 1090 1110

Stat

ic W

ater

Lev

el (

mam

sl)

Elevation (mamsl)

SWL(mamsl)

SWL(mamsl)

Linear (SWL(mamsl))

Figure 8: Correlation Graph Including All Boreholes

5.6 POTENTIAL CONTAMINANTS

The major contaminant associated with the proposed mining activities emanate from tailings dams,

waste rock dumps, open pit voids/walls and metallurgical processing plants. The contaminants are

dominated by elevated ion, metals and sometimes low pH. The mobility and concentrations of most

metals in the subsurface is likely to be governed by pH.

In general, contaminated water characterised by a low pH formed as a result of sulphide oxidation,

contribute to the mobility of metals. It may be possible that due to certain buffer reactions, the pH

of the contaminated water has normalised. However, certain constituents are still found in

elevated levels.

Workshops and fuel and oil handling facilities are likely sources of hydrocarbon related

contaminants. Oils, grease and other hydrocarbon products (such as petrol and diesel) handled in

these areas may contaminate the environment by spillages and leakages. Oils and greases are

removed and collected in oil traps. Run-off (contained with hydrocarbons) which is not collected

may enter the storm water system from where it may contaminate surface water bodies and

groundwater.

Septic tanks and sewage treatment plants potentially contaminate groundwater. Contaminants

associated with these plants include coliforms (e.g. E.coli), bacteria viruses, ammonia, phosphate,

sulphate and nitrate. Effluent from these systems usually contains elevated concentrations of

organic matter which may lead to elevated COD and BOD. Waste disposal areas may source a wide

range of contaminants, ranging from metals, organic matter, hydrocarbons, phosphates, etc.



5.6.1 Acid generation capacity of the rock

The acid generation capacity of three core samples was determined by acid-base accounting. The

samples were taken from exploration borehole GVN 132 M drilled in the ore body. The depth of

sampling for the three core samples analysed is summarised in Table 7. Analyses were performed by

Waterlab, Pretoria, and the results are presented in Table 8.

Table 7: Sampling Depths for ABA

Sample Number Sample depth (m)

GVN 132 M - A 12.23 - 12.35

GVN 132 M - B 51.66 - 51.95

GVN 132 M - C 76.77 - 76.90

Table 8: Results of Acid Base Accounting

Acid – Base Accounting

Modified Sobek (EPA-600)

Sample No.

GVN 132 M-A GVN 132 M-B GVN 132 M-C

Paste pH 7.3 9.3 9.7

Total Sulphur (%) (LECO) 0.01 2.04 0.75

Acid Potential (AP) (kg/t) 0.313 63.75 23.44

Neutralization Potential (NP) 4.45 9.90 5.45

Nett Neutralization Potential (NNP) 4.15 0.00 0.00

Neutralization Potential Ratio (NPR) (NP:AP) 14 0.155 0.232

Rock Type II I I

Table 9: Material Type Classification

TYPE I Potentially Acid Forming Total S(%) > 0.25% and AP:NP ratio 1:1 or less

TYPE II Intermediate Total S(%) > 0.25% and AP:NP ratio 1:3 or less

TYPE III Non-Acid Forming Total S(%) < 0.25% and AP:NP ratio 1:3 or greater

It follows from Table 9 that the tailings can be generally classified as TYPE I (samples deeper than

51 m) and TYPE II (sample taken at approximately 12 m depth) material that is considered to be



intermediate to potentially acid forming. The neutralisation potential for the TYPE I samples are

much lower than the TYPE II sample and the sulphur content is also higher. The sample GVN 132 M-

A was collected at a shallow depth as a result any sulphides are likely to have been oxidised due to

weathering.

If the results are judged against the latest screening criteria developed at the IGS of the UFS16, the

following is concluded:

The two deeper samples (GVN 132 M-B and C) exceed the limit of 0.3% sulphide (S), and is

thus regarded to contain sufficient oxidisable sulphide to sustain acid generation.

With a NPR ratio below 1:1 it is likely that acid can potentially be generated from the

deeper rock.

The paste pH as seen in Table 8 indicates relative neutral or alkaline conditions, which is in

contrast with the the acid potential (AP) and Neutralization Potential Ratio (NPR) (NP:AP). The

most likely explanation is that the sulphides found in the rock are not that reactive, or the sulphide

minerals found in the rock are not that reactive. Some sulphide minerals such as Pyrite, Pyrrhotite,

Chalcopyrite and Pentlandite are known to potentially generate acid when oxidised. The Total

Sulphur (%) is used to calculate the AP, however no differentiation is made between the different

sulphide minerals. Only once the mineralogical composition of the rocks are known, deductions can

be made in terms of the acid generation potential of the rock. The mineralogical compositions can

be determined by means of XRD/XRF analyses and may become available from a metallurgical

study.

5.6.2 Leach test

The core samples were also analysed for leachable major metals. The distilled water leach test17 is

a method recommended by DWAF in the Minimum Requirements for the Handling and Disposal of

Hazardous Waste17. The analytical results can be seen in Table 10. The analytical results show

certain metals to leach from the rock under the laboratory conditions. The metals include: iron,

barium, cobalt, chromium, copper, nickel, tin, manganese and aluminium. Traces of zinc and lead

were also identified.

16 Usher, B H et al: On-site and Laboratory Investigations of Spoil in Opencast Collieries and the Development

of Acid-Base Accounting Procedures. Institute for Groundwater Studies of the University of the Free State.

17 DWAF. 2006. Minimum Requirements for the Handling, Classification and Disposal of Hazardous Waste. (3rd

Ed). Department of Water Affairs and Forestry, Pretoria.



Table 10: Analytical results of distilled water leach test of the core samples

Sample No. GVN 132 M-A GVN 132 M-B GVN 132 M-C

Ag 0.432 0 1.484

Al 22.92 0 284

As 0 0 0

B 0 0 0.204

Ba 2.904 0 9.24

Be 0 0 0

Bi 0 0 0

Ca 48 20 320

Cd 0 0 0

Co 1.104 0 0.304

Cr 2.56 0 11.32

Cu 1.456 0 5.08

Fe 160 2.84 864

K 18 72 108

Li 0 0 0

Mg 328 16 1008

Mn 11.96 0 21.92

Mo 0 0 0

Na 28 116 440

Ni 4.56 0 5.96

P 0.708 0 2.172

Pb 0.128 0 0.628

S Sb 0 0 0

Se 0 0 0

Si 196 64 288

Sn 30.56 0.548 176

Sr 1.012 0.216 10.32

Ti 0 0 1.36

V 0 0 1.124

W 0 0 0

Zn 0.132 0 0.612

Notes:

Concentrations are in mg/kg



5.6.3 Acid rock drainage (ARD) formation

The reactions of acid and sulphate generation from sulphide minerals are discussed according to

the three stage stoichiometric example of pyrite oxidation after James, (1997) and (Ferguson &

Erickson, 1988) in which one mole of pyrite oxidized forms two moles of sulphate:

Reaction (2.1) represents the oxidation of pyrite to form dissolved ferrous iron, sulphate and

hydrogen. This reaction can occur abiotically or can be bacterially catalysed by Thiobacillus

ferrooxidans.

FeS2 +7/2 O2 + H2O 2+ + 2SO42- + 2H+ (2.1)

The ferrous iron, (Fe2+) may be oxidised to ferric iron, (Fe3+) if the conditions are sufficiently

oxidising, as illustrated by reaction (2.2). Hydrolysis and precipitation of Fe3+ may also occur,

shown by reaction (2.3). Reactions (2.1), (2.2) and (2.3) predominates at pH > 4,5.

e2+ + 1/4O2 + H+ 3+ + 1/2H2O (2.2)

Fe3+ + 3H2 3 (s) +3H+ (2.3)

Reactions (2.1) to (2.3) are relatively slow and represent the initial stage in the three-stage ARD

formation process. Stage 1 will persist as long as the pH surrounding the waste particles is only

moderately acidic (pH > 4,5). A transitional stage 2 occurs as the pH decreases and the rate of Fe

hydrolyses (reaction 2.3) slows, providing ferric iron oxidant. Stage 3 consists of rapid acid

production by the ferric iron oxidant pathway and becomes dominant at low pH, where the Fe2+

(ferric iron) are more soluble (reaction 4):

FeS2 + 14 Fe3+ + 8H2O 2+ + 2SO42- + 16H+ (2.4)

Without the catalytic influence of the bacteria, the rate of ferrous iron oxidation in an acid

medium would be too slow to provide significant ARD generation. As such the final stage in the ARD

generation process occurs when the catalytic bacteria Thiobacillus ferrooxidans have become

established. Reactions (2.2) and (2.4) then combine to form the cyclic, rapid oxidation pathway

mainly responsible for the high contamination loads observed in mining environments.

5.7 WATER QUALITY

Eighteen groundwater samples and one surface water sample from the Nyl River were collected

from selected boreholes indentified during the hydrocensus. Water samples were also collected

from the five newly drilled boreholes. The water samples were submitted for major cation and

anion analyses to an accredited laboratory, the certificate of analyses can be seen in Appendix E.

5.7.1 Quality control

A duplicate sample was collected from one of the boreholes, VOL22. The duplicate sample were

renamed and submitted to the laboratory. The accuracy of the laboratory analysis of the samples

was measured by means of calculating the Relative Percent Difference (%RPD):



%100

2/21

21%

DD

DDRPD

Where: D1 = parent sample concentration

D2 = duplicate sample concentration

Relative Percent Differences (RPDs) provide a measure of the precision of the laboratory results,

and have been calculated for the analytical results of the duplicate water sample. RPDs are

calculated as the percentage of the difference between two duplicate samples divided by the

average of the two duplicate samples. GPT specifies an acceptable RPD level of <20% where

analytes are detected in the same order of magnitude as the detection limits. It was found that all

constituent concentrations were at the acceptable RPD level. The samples can thus be used for

interpretation with a high degree of accuracy and certainty.

Table 11: Analysis results of duplicate samples

NO3 Cl Ca Mg

VOL22 292.04 76.00 53.77 151.69

VOL22 Dupl 265.09 78.40 47.29 132.13

% RPD 0.10 0.03 0.13 0.14

5.7.2 Water quality discussion

The results of the water chemical analyses are contained in Table 12 and Table 13, and compared

to the SABS Drinking Water Standards (SANS 241:2006, Ed. 6.1) as the potential receptor of concern

is groundwater users. Colours of individual cells refer to the drinking water classification of the

specific water sample. The results of these analyses were depicted as pie diagrams (circular graphs

as in Figure 9) and Stiff diagrams (Figure 10).

The pie diagrams (Figure 9) show both the individual ions present in a water sample and the total

ion concentrations in meq/L or mg/L. The scale for the radius of the circle represents the total ion

concentrations, while the subdivisions represent the individual ions. It is very useful in making

quick comparisons between waters from different sources and presents the data in a convenient

manner for visual inspection.

A Stiff diagram (Figure 10) is basically a polygon created from four horizontal axes using the

equivalent charge concentrations (meq/L) of cations and anions. The cations are plotted on the

left of the vertical zero axis and the anions are plotted on the right. Stiff diagrams are very useful

in making quick comparisons between waters from different sources.18

18 EAS 44600 Groundwater Hydrology, Lecture 14: Water chemistry 1, Dr Pengfei Zhang



On the Piper diagram (Figure 11) the cation and anion compositions of many samples are

represented on a single graph. Certain trends in the data can be discerned more visually, because

the nature of a given sample is not only shown graphically, but also show the relationship to other

samples. The relative concentrations of the major ions in percent Meq/L or percent mg/L are

plotted on cation and anion triangles, and then the locations are projected to a point on a

quadrilateral representing both cation and anions.

The groundwater quality of almost all samples contained constituent concentrations that exceed

the maximum allowable standard for domestic use (SANS 241)19. Only the water quality in borehole

GV1 complies with the standard. The borehole VOL1, ABDUL and the sample from the Nyl River

partially comply with the standard with just elevated magnesium, iron and manganese

concentrations, respectively. Constituents found in concentrations that exceed the standard

include magnesium, nitrate and chloride. As a result of these elevated constituents, electrical

conductivity and total dissolved solids levels are thus elevated as can be seen from the results

especially borehole BOK8 which also showed elevated concentrations of calcium.

Elevated nitrate levels were detected in VOL17, VOL19, VOL20, VOL21 and VOL22 and it is primarily

a health concern in that it can be readily converted in the gastrointestinal tract to nitrite as a

result of bacterial reduction.

The pie diagrams (Figure 9) confirm the boreholes DEK1, BOK1, BOK8, VOLS1, VOLS3, VOLS5 as the

samples with the most elevated total constituent concentrations with Cl contributing for the most

part. Other major contributing constituents identified are NO3, Mg, Na, Ca and SO4. Nitrate (NO3) is

found in most sampled boreholes; the most likely source is fertilizers. The NO3 is transported

vertically with infiltrating water. The elevated Cl concentrations may be attributed to induced

salinity of the groundwater from irrigation practices.

The stiff diagrams (Figure 10) and piper diagram (Figure 11) show that the general water type of

the boreholes on the farm Volspruit is Mg-Ca/HCO3. The water type for the boreholes south of

Volspruit Portion 1 on Volspruit Portion 2 are Mg-Ca/Cl, while on the farm Bokpoort Mg-Na/Cl type

water is found. The boreholes located north of Volspruit show a Mg-Ca/HCO3 –Cl type signature. The

sample taken from Nyl River plots uniquely on the piper diagram as a Na-Mg/HCO3-Cl water type.

Since the samples were taken after the rain season the water chemistry signature differs between

the river and groundwater as the river has been sourced by runoff from different areas. The

chemistry analyses supplied within this report should serve as baseline water quality throughout the

life of the proposed mining operations.

19 South African Bureau of Standards document “Specification: Drinking Water” SANS 241 Ed. 6.1

2006



Table 12: Results of Major Cation and Anion Analyses

Sample Nr. ABDUL BOK1 BOK8 DEK1 GV1 GV5 GV7 GV8 NYL1 Class I Class IICa 46.07 185.97 341.11 129.91 24.42 78.23 78.90 10.13 5.58 150 300

Mg 73.61 152.24 188.66 145.73 63.40 122.48 83.28 121.21 4.08 70 100

Na 33.20 232.80 90.32 209.16 23.30 26.70 28.28 46.39 15.90 200 400

K 5.21 5.22 5.67 5.21 1.69 1.91 3.01 28.35 4.61 50 100

Mn 0.01 0.01 0.03 0.01 0.01 0.01 0.01 0.07 0.00 0.1 1

Fe 0.00 0.00 0.02 0.00 0.01 0.01 0.00 0.00 0.26 0.2 2

F 0.00 0.00 0.00 0.51 0.00 0.00 0.00 0.00 0.00 1 1.5

NO3 0.75 35.37 46.37 48.75 43.49 63.87 21.66 0.00 0.00 44 88

NH4 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.89 0.00 1 2

Al 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.13 0.3 0.5

PO4 0.00 0.18 0.00 0.25 0.13 0.00 0.00 0.00 0.00 - -

HCO3 463.10 346.60 139.71 387.16 309.23 283.33 340.98 349.90 50.38 - -

Cl 51.30 886.30 1228.20 716.80 39.30 370.80 224.50 259.50 20.30 200 600

SO4 18.46 71.90 128.26 117.07 18.42 10.42 30.69 16.17 4.32 400 600

TDS by sum 457.00 1713.00 2061.00 1526.00 333.00 766.00 622.00 665.00 80.00 1000 2400

M-Alk(CaCO3) 381.00 284.90 114.70 318.20 254.90 234.80 280.80 305.80 41.40 - -

pH 7.59 7.47 7.22 7.45 7.77 8.06 7.69 8.84 7.39 5.0 - 9.5 4.0 - 10.0

EC 112.90 346.50 384.00 279.80 70.80 160.90 124.20 126.60 13.15 150 370

Cat/An Bal. % 2.42 -1.09 -4.86 -3.67 1.36 -3.84 -3.36 -1.84 -1.42 - -

na- not analysed

All concentrations are presented in mg/l, EC is presented in mS/m

0 = below detection limit of analytical technique

Exceeding maximum allowable standard for domestic use

Class II

Class I

Notes:



Table 13: Results of Major Cation and Anion Analyses (continued)

Sample Nr. VOL1 VOL13 VOL17 VOL19 VOL20 VOL21 VOL22DUPL. VOL22 VOLS1 VOLS3 VOLS5 Class I Class II

Ca 9.82 62.47 54.93 47.53 52.91 32.40 53.77 47.29 39.48 82.01 51.38 150 300

Mg 41.98 110.49 104.77 139.86 141.29 101.10 151.69 132.13 157.32 231.53 130.25 70 100

Na 20.17 18.68 12.95 13.95 12.40 11.71 13.77 12.76 62.76 95.26 107.69 200 400

K 6.71 4.10 5.56 5.37 4.42 5.60 5.54 5.27 4.43 4.78 3.27 50 100

Mn 0.32 0.01 0.04 0.01 0.02 0.06 0.03 0.04 0.01 0.01 0.00 0.1 1

Fe 0.25 0.00 0.02 0.01 0.02 0.02 0.01 0.03 0.00 0.00 0.00 0.2 2

F 0.00 0.00 0.60 0.23 0.22 0.27 0.71 0.66 0.26 0.48 0.00 1 1.5

NO3 0.00 58.24 125.97 271.38 132.18 169.05 292.04 265.09 26.62 46.18 31.52 44 88

NH4 0.00 0.00 0.05 0.11 0.08 0.06 0.04 0.04 0.00 0.00 0.00 1 2

Al 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.3 0.5

PO4 0.12 0.14 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.15 - -

HCO3 272.36 458.26 359.71 313.03 586.41 309.07 349.69 346.98 384.80 429.99 469.24 - -

Cl 16.80 92.40 58.20 68.80 44.50 42.10 76.00 78.40 397.70 704.40 353.10 200 600

SO4 4.67 50.09 65.42 93.05 59.22 60.98 121.11 98.75 50.15 94.52 55.56 400 600

TDS by sum 235.00 578.00 509.00 584.00 634.00 445.00 660.00 607.00 908.00 1435.00 940.00 1000 2400

M-Alk(CaCO3) 225.60 378.40 298.40 257.40 482.80 254.40 287.80 287.40 317.40 353.40 386.50 - -

pH 8.04 7.89 8.10 7.52 7.67 7.64 7.63 8.04 7.82 7.45 7.71 5.0 - 9.5 4.0 - 10.0

EC 48.20 126.50 97.20 127.30 123.00 92.40 141.50 141.10 183.60 278.90 186.50 150 370

Cat/An Bal. % -0.65 3.81 4.65 4.38 2.22 1.59 2.51 -1.28 -3.48 -3.93 -3.50 - -

na- not analysed

All concentrations are presented in mg/l, EC is presented in mS/m

0 = below detection limit of analytical technique

Exceeding maximum allowable standard for domestic use

Class II

Class I

Notes:



Figure 9: Pie Diagrams of Groundwater and Surface Water Chemistry



Figure 10: Stiff Diagrams of Groundwater and Surface Water Chemistry



Figure 11: Piper Diagram



5.7.3 Discussion of groundwater chemistry and health risks

From the chemistry analysis of the water samples collected from the boreholes, magnesium, nitrate

and chloride were the chemical substances found not to comply with SANS 241 drinking water

standard. The health risks to humans20 were obtained from the DWAF water quality guidelines and

were summarised in Table 14. At the levels of magnesium found in the water, no major health or

aesthetic effects are likely.

Table 14: Summary of the Human Health Risks Posed by the Relevant Constituents

Elevated

element

Groundwater/surface

water samples

Human Health effects at current

concentrations

Nitrate

BOK1, BOK8, DEK1, GV1,

GV5, VOL13, VOLS1,

VOLS3, VOLS5, VOL17,

VOL19, VOL20, VOL21,

VOL22.

Concentrations above 20 mg/l cause

methaemoglobinaemia in infants and mucous

membrane irritation in adults.

Chloride BOK1, BOK8, DEK1, VOLS3

Water aesthetically unacceptable due to a

salty taste and may cause nausea, a

disturbance of electrolyte balance and

dehydration especially in infants ( >1200 mg/l).

20 DWAF 1996, South African water Quality Guidelines, volume 1, domestic use



6 GROUNDWATER VULNERABILITY

According to Lynch et al. aquifer vulnerability is defined as the intrinsic characteristics that

determine the aquifer’s sensitivity to the adverse effects resulting from the imposed pollutant21.

The following factors have an effect on groundwater vulnerability:

Depth to groundwater: Indicates the distance and time required for pollutants to move

through the unsaturated zone to the aquifer.

Recharge: The primary source of groundwater is precipitation, which aids the movement of

a pollutant to the aquifer.

Aquifer media: The rock matrices and fractures which serve as water bearing units.

Soil media: The soil media (consisting of the upper portion of the vadose zone) affects the

rate at which the pollutants migrate to groundwater.

Topography: Indicates whether pollutants will run off or remain on the surface allowing for

infiltration to groundwater to occur.

Impact of the vadose zone: The part of the geological profile beneath the earth’s surface

and above the first principal water-bearing aquifer. The vadose zone can retard the

progress of the contaminants21.

The Groundwater Decision Tool (GDT) was used to quantify the vulnerability of the aquifer

underlying the site. The depth to groundwater below the site was estimated from water levels

measured during the hydrocensus and borehole drilling inferred to be ~20 mbgl at the site. A

groundwater recharge of 3.2%, a sandy clayey-loamy clay soil and a gradient of 1.15% were assumed

and used in the estimation. The GDT calculated a vulnerability value of 45%, which is moderate or

medium. This implies that the aquifer is reasonably sensitive to contamination and care should be

taken with any activities that could generate pollutants.

21 The South African Groundwater Decision Tool (SAGDT), Manual Ver. 1 (Department of Water Affairs and Forestry)



7 AQUIFER CLASSIFICATION

The main aquifers underlying the area were classified in accordance with the Aquifer System

Management Classification document22. The aquifers were classified by using the following

definitions:

Sole Aquifer System: An aquifer which is used to supply 50% or more of domestic water for a

given area, and for which there is no reasonably available alternative sources should the

aquifer be impacted upon or depleted. Aquifer yields and natural water quality are

immaterial.

Major Aquifer System: Highly permeable formations, usually with a known or probable

presence of significant fracturing. They may be highly productive and able to support large

abstractions for public supply and other purposes. Water quality is generally very good

(Electrical Conductivity of less than 150 mS/m).

Minor Aquifer System: These can be fractured or potentially fractured rocks which do not

have a high primary permeability, or other formations of variable permeability. Aquifer

extent may be limited and water quality variable. Although these aquifers seldom produce

large quantities of water, they are important for local supplies and in supplying base flow

for rivers.

Non-Aquifer System: These are formations with negligible permeability that are regarded as

not containing groundwater in exploitable quantities. Water quality may also be such that it

renders the aquifer unusable. However, groundwater flow through such rocks, although

imperceptible, does take place, and needs to be considered when assessing the risk

associated with persistent pollutants.

Based on information collected during the hydrocensus, it can be concluded that aquifer system in

the study area can be regarded as a major aquifer, based on the reliance of the surrounding water

users on groundwater. As part of the aquifer classification, a Groundwater Quality Management

(GQM) Index is used to differentiate the degree to which an aquifer should be protected In order to

achieve the GQM Index a points scoring system as presented in Table 15 is used to calculate the

GQM.

22 Department of Water Affairs and Forestry & Water Research Commission (1995). A South African Aquifer System Management Classification. WRC Report No. KV77/95.



Table 15: Ratings for the Groundwater Quality Management Classification System

Aquifer System Management Classification

Class Score

Sole Source Aquifer System:

Major Aquifer System:

Minor Aquifer System:

Non-Aquifer System:

Special Aquifer System:

6

4

2

0

0 – 6

Aquifer Vulnerability Classification

Class Score

High:

Medium:

Low:

3

2

1

The occurring aquifer(s) at the site, in terms of the above definitions, is classified as a sole aquifer

system, due the relative absence of surface water and heavy reliance on groundwater. The

vulnerability of the groundwater system in terms of the above is classified as medium (See section

6).

The level of groundwater protection based on the Groundwater Quality Management Classification:

GQM Index = Aquifer System Management x Aquifer Vulnerability

= 4 x 2 = 8

Table 16: GQM Index for the Study Area

GQM Index Level of Protection Study Area

<1

1 – 3

3 – 6

6 – 10

>10

Limited

Low Level

Medium Level

High Level

Strictly Non-Degradation

8

7.1 AQUIFER PROTECTION CLASSIFICATION

A Groundwater Quality Management Index of 8 was estimated for the study area from the ratings

for the Aquifer System Management Classification. Therefore the fractured aquifer should not be

negatively affected by contamination and should be protected.



Due to the high GQM index calculated for this area, a high level (no or little degradation of

groundwater quality) of protection is needed to adhere to DWAF’s water quality objectives.

Therefore reasonable and sound groundwater protection measures are recommended to ensure that

no cumulative pollution affects the aquifer, in the long term.



8 SITE CONCEPTUAL MODEL

The site conceptual model was developed using a risk based approach, whereby impact source

areas are identified, pathways are characterised and potential receptors identified. Both the

mining and post mining scenarios are addressed. In the mining phase, drawdown of the groundwater

level will be the main impact, while pollution emerging from the backfilled opencast is considered

the most important post mining impact.

8.1 IMPACT SOURCE

The potential impact source areas were identified as the following:

Opencast mine

Waste rock dumps

Tailings dams

Workshops and petroleum storage tanks

Septic tank

General waste facilities

The hydraulic characteristics of the source and the geochemical properties of the subsurface will

determine the behaviour of the contaminants emanating from the source. In addition, the location

and extent of the pollution source will have an effect on the extent of the contaminant plume.

8.1.1 Opencast mine

During mining the opencast will have to be dewatered to allow access to equipment and mining

personnel. Dewatering can be done by installing dewatering boreholes at the perimeter of the

mine, and/or dewatering from a sump(s) at the mine floor elevation, various other methods exist.

Regardless of the method used, the end result is that the local groundwater in and immediately

around the opencast will be at the elevation of the bottom of the ore body by end of mining.

The northern ore body is subdivided into a north-eastern section and a south-western section by a

fault with the south-western section downthrown by about 100 metres. Thus, while the bottom of

mining of the north-eastern section is predicted to be at 50 metres below ground level, the south-

western section could be as deep as 150 metres. This depression in the groundwater will result in a

cone of depression around the opencast, with the radius depending on the hydraulic conductivity of

the host material, as illustrated in Figure 12 below. Should the hydraulic conductivity be relatively

low, the cone of depression would be localised around the immediate vicinity of the mine, while a

high conductive bedrock material could result in the groundwater level being drawn down to below

the river.

Post mining, the groundwater will return to pre-mining levels, or even above pre-mining levels in

the lower sections of the opencast. This is due to the very high hydraulic conductivity of the

backfilled material in comparison to the undisturbed bedrock material that will tend to flatten the



water level in the opencast. Should the water level in the lower sections rise above the surface

level, decanting will result. Furthermore, normal groundwater flow from the backfilled opencast to

the river will resume. If the backfilled material is sulphide containing, these outflows will most

likely be contaminated with mainly sulphate and selected metals, and could also be acidic

depending on the neutralisation potential of the material and reactivity of the sulphides.

The contaminant generation potential is pronounced where the source minerals of contaminants

are in direct contact with water and oxygen underground. The opencast mining operations expose

reactive minerals to water and oxygen. Sulphides are the main minerals which react and contribute

to the formation of acid rock drainage (ARD).

Mining sections that are not in contact with groundwater flow paths i.e. flooded or stagnant

sections are unlikely to contribute to ARD formation. ARD formation may be enhanced and continue

at high rates if there are active flow paths through sections. Where water is flowing through moist

sections, ideal conditions for sulphide mineral oxidation exist.



Figure 12: Conceptual groundwater drawdown and flow model



8.1.2 Waste rock dumps

The major controlling factor of ARD in waste rock dumps is the wide distribution in the particle

sizes of waste material as it governs the dominant processes responsible for ARD generation. As

rainfall infiltrates into the rock dumps, fines are either washed out or consumed through sulphide

oxidation and neutralisation, while larger particles weather to smaller particles. Preferential flow

paths in the dump (between particles) may result in rapid drainage of water and thus reduce the

effectiveness of neutralisation. Oxygen diffusing into and circulating in voids between particles

together with water films covering particles provide optimum conditions for sulphide oxidation,

especially as the dumps are unsaturated. Dust originating from the rock dumps may also settle on

surface water bodies and contribute to pollution. Rock dumps have a large potential to generate

ARD due to more exposure to the atmosphere.

In general the material (soil horizon) underlying waste rock dumps have a lower permeability than

the material of the waste rock dump itself. As a result, percolation of infiltrating water through the

rock dump into the subsurface may be limited. The leachate generated from the dump will thus

contribute to surface runoff and contribute to seepage in the soil/weathered horizon. It can be

assumed that mounding of the phreatic surface (water table) in the rock dump will be pronounced,

thereby increasing outflow from the dumps. The soil below the rock may continue to act as a

secondary source even once the all the rock has been removed (although the removal of the rock

would be unlikely).

8.1.3 Tailings dams

These facilities usually consist of an unsaturated upper zone and saturated lower zone. In the

unsaturated zone oxygen penetrate to some depth and sulphide oxidation can occur. The saturated

zone forms due to infiltration resulting in a rise in the phreatic surface in the dams. The presence

of water in this zone suppresses chemical reactions.

The tailings is characterised by small particle size, resulting in large exposed surface area of

reactive minerals (sulphides). This enhances the rate of weathering processes resulting in the

formation of ARD leachate. Due to the fine particle size of the tailings, oxygen penetration in the

dam is limited in the saturated zone. Normally these dams do have an impact on the groundwater

quality. The soil below the dam is also likely to act as a secondary source of contamination.

8.1.4 Workshops, septic tanks and domestic waste disposal sites

Workshops, fuel dispensing areas, septic tanks and waste disposal sites may contribute to the

contamination potential of the mine. Hydrocarbons may be found in elevated levels in the soil,

groundwater and surface water in the area where they are handled (workshops and fuel dispensing

areas). Although waste disposal sites and septic tanks do not contribute largely to the potential

contaminant load of the proposed mine, they may impact in localised areas around the sites. The

potential impacts include groundwater, surface water and soil. It is currently unknown whether the

above mentioned contaminant sources will existed on the site and where they will be located.



8.2 PATHWAYS

Pathways along which contaminants may be mobilized and migrate toward groundwater receptors

include:

The vadose zone (unsaturated zone)

Groundwater (fractured aquifers)

Surface runoff in storm water or water courses (rivers and streams)

The scope of this study is however only to characterise the pathway of concern viz. groundwater.

Seepage from the tailings dams, waste rock dumps into the vadose zone and fracture systems of

deeper aquifers can lead to the contamination of groundwater and consequently water supply

boreholes. For accurate prediction of the behaviour of a contaminant plume along pathways it is

critical that the monitoring and field measurements are representative of the physical

environment. It is also important to keep seasonal and annual trends in mind as it affects the water

quality at the receptor.

8.2.1 Site specific hydrogeology

Although aquifers can vary considerably regarding geohydrological characteristics, they are seldom

observed as isolated groundwater systems. Usually they would be interconnected by means of

fractures, faults and intrusions. As mentioned in section 4.4, parts of the Northern Limb of the

Bushveld Complex is characterised by abundant faulting and elevated borehole yields. This

Volspruit project is located in one of the uncharacteristically highly fractured parts of the Northern

Limb. Therefore the hydrogeological conceptualisation of this project is different from

conventional Bushveld Complex conceptual model. Observations made by Genmin in 1990 found the

core to be heavily fractured with extensive serpentinised alteration, which may indicate the flow of

water along these structures.14 It was further mention in that study14 that water related problems

were found during the operation of the Grasvally chrome mine which lies 3km north of the project

area. An observation made in the study was that borehole yields became more reliable and

sustainable towards the south inferred to be the result of increased fracturing near the Zebediela

fault, this was however not substantiated. The study found the water table to be fairly flat in the

project, due to the high transmissivity of the subsurface and relatively shallow (~20-~37mbgl) over

abstraction of groundwater.14

The rocks appear to be fractured and weathered below most of the site to a depth of 50-60mbgl as

deduced in section 4.3.1. This finding is also substantiated by the groundwater study in 199014.

Therefore the top 50m of the rock profile defined by weathering and fracturing is characterised by

intergranular and fracture flow. Groundwater flow and storage is likely occurs in the fractures and

matrix. As the weathering decreases with depth, fracturing becomes dominant over weathering.

Flow and storage of groundwater therefore occurs in fractures in the rock mass.

The faults in the project area act as conduits and are associated with large volumes of groundwater

as substantiated by the hydrocensus and borehole drilling on the faults. A borehole targeted on a



zone of deep weathering also had a high yield (sustainably pumped at 6l/s), this borehole was

drilled near the Nyl River.

The Nyl River and alluvial sediments are likely to be hydraulically connected to the weathered and

fractured aquifer. This could however not be substantiated by the waters geochemical signatures

due the recent rainfall at the time of sampling. Although different aquifers units are likely to be

found, they are inferred to be hydraulically connected with each other. It can said that the aquifers

are likely to be recharged by rainfall and the Nyl River.

8.3 RECEPTORS

Any user of a groundwater or surface water resource that is affected by drawdown of the

groundwater level or pollution from any of the above mentioned sources, is defined as a receptor.

The following receptors may be found:

Groundwater users by means of borehole abstraction

Water courses: water users, fauna and flora.

The main water uses in the vicinity of the mine are domestic and agricultural, while the nearby Nyl

River is a sensitive water course with several wetlands upstream and downstream.

The river is likely to be gaining and losing river depending on the season. A lowering of the

groundwater level could result in a local reduction of inflow to the river. Furthermore,

contaminated surface and groundwater is likely to impact on the river water quality. If the river is

gaining after mine closure then potential pollution emanating from the mine activities may impact

on the river.

The primary receptors of groundwater in this area are irrigation and domestic users. The potential

receptors may be impacted on in terms of groundwater quality and/or quantity can be seen in

Table 17. It must noted that no access was gained to the property immediately south of Volspruit

326 KP Portion 2 owned by Mr. M. Mazzaro.



Table 17: Potential Receptors

Borhole Number

Owner Use Static water level

(mbgl) Farm name

ABDUL Abdulla Irrigation 6.18 Rondeboschje 295 KR

GV5 K. Kusbach Domestic 28.8 Grasvally293KR

GV6 Mine Domestic no access Grasvally293KR

GV7 Not at home Irrigation 23.42 Grasvally293KR

GV8 Niemcor Irrigation 37.75 Zoetveld 294 KR

VOLS1 D. De Beer domestic and

Irrigation 27.85 Volspruit 326 KP Portion 2

VOLS2 D. De Beer Irrigation no access Volspruit 326 KP Portion 2

VOLS3 D. De Beer Irrigation 23.81 Volspruit 326 KP Portion 2

VOLS4 D. De Beer Not in use 24.3 Volspruit 326 KP Portion 2





VOLS9 D. De Beer Not in use 10.7 Volspruit 326 KP Portion 2



BOK1 J. De Klerk Domestic 7.53 Bokpoort 328 KR

BOK2 J. De Klerk Domestic no access Bokpoort 328 KR

BOK3 J. De Klerk Domestic 11.88 Bokpoort 328 KR



9 NUMERICAL MODEL

It is the aim of this chapter to determine the implication that the groundwater might have on the

proposed opencast mining, and to assess the likely hydrogeological impact that the mining

operations might have on the receiving environment.

Numerical groundwater modelling is considered to be the most reliable method of anticipating and

quantifying the likely impacts on the groundwater regime. The model construction will be

described in detail in the following paragraph, followed by predicted impacts in terms of

groundwater quality and quantity for the relevant mining phases.

The finite difference numerical model was created using the US Department of Defence

Groundwater Modelling System (GMS Version 7.0.3, build date Feb 22, 2010) as Graphical User

Interface (GUI) for the well-established Modflow and MT3DMS numerical codes.

MODFLOW is a 3D, cell-centred, finite difference, saturated flow model developed by the United

States Geological Survey. MODFLOW can perform both steady state and transient analyses and has

a wide variety of boundary conditions and input options. It was developed by McDonald and

Harbaugh of the US Geological Survey in 1984 and underwent several overall updates since. The

latest update (Modflow 2000) incorporates several improvements extending its capabilities

considerably, the most important being the introduction of the new package called the Layer-

Property Flow Package.

MT3DMS is a 3-D model for the simulation of advection, dispersion, and chemical reactions of

dissolved constituents in groundwater systems. MT3DMS uses a modular structure similar to the

structure utilized by MODFLOW, and is used in conjunction with MODFLOW in a two-step flow and

transport simulation. Heads are computed by MODFLOW during the flow simulation and utilized by

MT3DMS as the flow field for the transport portion of the simulation.

The structure of the remainder of this report is divided into the following main sections:

Construction of the numerical model, including a description of the boundaries used and

subdivision of the model into discrete finite difference cells.

Prediction of the groundwater drawdown due to dewatering at the Volspruit Northern Pit.

9.1 FLOW MODEL CONSTRUCTION

In this paragraph the setup of the flow model will be discussed in terms of the conceptual model as

envisaged for the numerical model, elevation data used, boundaries of the numerical model and

assumed initial conditions.

9.1.1 Elevation data

Elevation data is crucial for developing a credible numerical model, as the groundwater table in its

natural state tends to follow topography. The best currently available elevation data is derived



from the SRTM (Shuttle Radar Tomography Mission) DEM (Digital Elevation Model) data. The SRTM

consisted of a specially modified radar system that flew on board the Space Shuttle Endeavour

during an 11-day mission in February of 2000, during which elevation data was obtained on a near-

global scale to generate the most complete high-resolution digital topographic database of Earth23.

Data is available on a grid of 30 metres in the USA and 90 metres in all other areas. The data points

in the Volspruit mining area are shown in Figure 14 below. It should be emphasised that this figure

is not derived from satellite photography, but is purely a 3-D presentation of the elevation data.

The accuracy and density of the data is deemed adequate in relation to the size of the Volspruit

opencast areas.

This data has been used for delineating the model area as depicted in Figure 14. Due to the density

of data it is not possible to picture the points over the whole modelled area. In total, 102 000

elevation data points define the model topography.

Several studies have been conducted to establish the accuracy of the data, and found that the data

is accurate within an absolute error of between 2 and 4 metres for Southern Africa24. Over a limited

area, as in this study, the relative error compared to neighbouring point is expected to be less than

one metre. This is adequate for the purpose of a numerical groundwater model, especially if

compared to other uncertainties; and with the wealth of data this results in a much improved

model.

23 http://www2.jpl.nasa.gov/srtm/

24 Rodriguez, E., et al, 2005. An assessment of the SRTM topographic products. Technical Report JPL D-31639, Jet Propulsion Laboratory, Pasadena, California.



Figure 13: SRTM Elevation Points



Figure 14: SRTM Elevation Data



9.1.2 Lateral Boundaries

To simulate the groundwater conditions that will be affected by the proposed pit, the aquifer has

been modelled as described below. Boundaries were chosen to include the area where the

groundwater drawdown could reasonably be expected to spread and simultaneously include as

many natural groundwater boundaries as possible.

Wherever practical, natural topographical water divides are normally used as no-flow boundaries,

assuming that the groundwater elevation follows the topography. Inspection of the topography data

as described above revealed that the area is indeed bounded by well-positioned natural boundaries,

depicted in Figure 15 below. Natural water divides were used as no-flow boundaries in the eastern

and western extents of the model. In the north and south, the model was terminated with parallel

flow boundaries, on the assumption that groundwater will flow perpendicular to the surface

contours. A small inflow and outflow area in the south and north, coinciding with the Nyl River, was

used as a constant head boundary at an elevation of 5 metres below ground level.

These boundaries resulted in a modelled area of about 5 to 15 km around the proposed Volspruit

Northern Pit, which is considered far enough apart for the expected groundwater effects not to be

influenced by the boundaries.

The modelling area was discretizised by a 220 x 200 grid refined at the Volspruit Pit, resulting in

finite difference elements of about 50 x 50 metres at the Pit increasing to somewhat more than one

kilometre square. All modelled features, like mining areas, etc., are sizably larger than these

dimensions, and the grid is thus adequate for the purpose. Nevertheless, the total amount of active

cells over all layers added up to about 20 000, resulting in a relatively large model.

9.1.3 Vertical Delineation

For the purpose of this study, the subsurface was conceptually envisaged to consist of the following

hydrogeological units:

The upper few meters below surface consist of completely weathered material. This layer

is anticipated to have a reasonable high hydraulic conductivity, but in general unsaturated.

However, in the immediate vicinity of proposed tailing dams and waste rock dumps the

groundwater level is kept close to surface due to the availability of water, and this layer is

probably at least partially saturated. Furthermore, a seasonal aquifer perched on the

bedrock probably also forms in this layer, especially after high rainfall events. Flow in this

perched aquifer is expected to follow the surface contours closely and emerge as fountains

or seepage at lower elevations.

The next few tens of meters are slightly weathered, fractured bedrock with a low hydraulic

conductivity. The permanent groundwater level resides in this unit and is about 2 to 10

meters below ground level. The groundwater flow direction in this unit is influenced by

regional topography and for the site flow would be in general northerly from high lying

areas.



Below a few tens of meters the fracturing of the aquifer is less frequent and fractures less

significant due to increased pressure. This results in an aquifer of lower hydraulic

conductivity and slower groundwater flow velocities.

Fracturing of the bedrock could consist of both major fault structures and/or minor pressure-

relieve joints. On a large enough scale (bigger than the Representative Elemental Volume) the

effect of these structures become less important and has been considered as a relative

homogeneous aquifer in this study.

The following assumptions and simplifications were made in constructing the numerical model:

The upper completely weathered aquifer perched in the bedrock is mostly unsaturated over

the study area. Although it is an important part of the hydrogeological system in this area

in the mining areas, it has not been modelled as a separate component as this will result in

abundant dry cells and consequential numerical instability. It has thus been grouped into

the upper layer of the model.

The bedrock has been modelled as five layers of decreasing hydraulic conductivity and

specific yield. Fractures in bedrock close up at depth, which result in a lowering of the

hydraulic conductivity25.

The local effect of discontinuities, such as faults, fractures and intrusions, has been

disregarded. Pumping test has indicated highly conductive areas not only at fault locations,

but also in seemingly un-faulted areas.

Laterally there is also no indication that faulting is limited to the ore body. With reference

to Figure 3, it can be seen that faults are found throughout the valley. It is therefore

unlikely that the highly transmissive aquifer is confined to the major faulting zones or the

ore body, and was therefore applied to the entire modelled area.

To ensure that the Volspruit model is not restrictive in depth, a total depth of 250 metres was

modelled, which is well below the lowest elevation of 150 metres below surface for the planned

pit. The model was subdivided in five layers of 50 metres each to fully exploit the 3D capabilities of

the modelling software and to include flow from both the sides and through the bottom of the

excavated pit.

Pump tests generally supply valuable information on the hydraulic conductivity of the subsurface.

However, unless sections of the borehole are sealed off with packers, this information is an average

value for the borehole. Thus, hydraulic conductivity (or alternatively, transmissivity) derived from

pump tests cannot be extensively used in 3D numerical simulations.

If suitable geotechnical borehole logs are available, the RQD (rock quality designation) is a very

helpful tool to derive the variation of conductivity with depth. In a study26, it was found that the

25 Barnes, S. L. et al. Coal Mine Drainage Prediction and Pollution Prevention in Pennsylvania. Pennsylvania

Department of Environmental Protection.

26 Gates, William C. B. The Hydro-Potential (HP) Value: a Rock Classification Technique for Estimating

Seepage into Excavations



RQD is directly proportional to the hydro-potential (HP) value, which is defined as the potential for

a rock mass to hydraulically transmit groundwater.

In the Volspruit geotechnical study, a few boreholes were logged for RQD, as illustrated in Figure 1.

The calculated HP values are remarkably similar for the logged boreholes and correlates reasonably

well with the core recovery values. It thus seemed to be the best indicator of variation of hydraulic

conductivity with depth, given the available data. It follows from this graph that RQD varies rapidly

from close to zero at surface, and stabilise at a value of about 80% at a depth of about 50 metres

below ground level. This correlates very well with another finding25 that the hydraulic conductivity

due to fracturing resulting from stress release of bedrock, varies by an order of magnitude for every

50 metres below surface.

Given the RQD values calculated for the Volspruit project, it was thus decided to allocate hydraulic

conductivities to the layers as shown in Table 18 below. In essence, the hydraulic conductivity of

the middle two layers has been taken half of that of the upper layer, while that of the lower two

layers have been halved again. As no boreholes penetrated to depths exceeding 150 metres, this

further halving of the hydraulic conductivity of the lower layers is an assumption. However, it is a

reasonable assumption25 and, as no mining is anticipated below 150 metres, the assumed values will

only influence inflow through the mine floor. The ideal would be to conduct detailed packer tests

in freshly drilled core boreholes in future to increase the accuracy of this assumption.

9.2 FIXED AQUIFER PARAMETERS

Hydraulic conductivity is probably the most important aquifer parameter for which a sound value

needs to be established. For this model less reliance has been placed on calibration to determine

hydraulic conductivity, while results obtained from pump testing was considered the best to use.

This was a result of the very flat water table over the study area that did not favour calibration

techniques. However, extensive pump test were done and values obtained from these was

considered the most reliable available at the time of the study (Table 18 and Table 19).

The remaining aquifer parameters normally have to be calculated and/or judged by conventional

means. The following values were used:

Recharge = 20 mm/a ≈ 0.00006 /d. This value was calculated using the RECHARGE

program27 and the chloride method as described earlier in this report. This value relates to

a recharge percentage of 3.2%, very close to the general accepted value of 3% for the South

African Highveld28. Please note that this is not effective recharge, as evapotranspiration

was also modelled as discussed below. The result will thus be higher recharge in high

topographical areas and lower recharge where the water table is shallow, similar to the

conditions in nature.

27 Gerrit van Tonder, Yongxin Xu: RECHARGE program to Estimate Groundwater Recharge, June 2000. Institute for Groundwater Studies, Bloemfontein RSA. 28 Vermeulen P D, Usher B H: An investigation into recharge in South African underground collieries. The

Journal of the Southern African Institute of Mining and Metallurgy, Vol. 106 Nov 2006.



Maximum Evapotranspiration = 1770 mm/a ≈ 0.0048 m/d. This value is based on the E-pan

evaporation data for this area29 as shown in Table 1. Note that this rate of

evapotranspiration is used by the modelling software only if the groundwater should rise to

the surface. For the groundwater level between the surface and the extinction depth, the

evapotranspiration is calculated proportionally.

Evapotranspiration Extinction Depth = 2 m. This depth relates to the expected average root

depth of plants in this area.

The specific yield and storage over the area was taken as 0.01 and 0.0001 respectively, as

calculated from the pump test data as documented in Table 18 below.

Hydraulic Permeability of the mined out and rehabilitated opencast area = 1 m/d. This is

two orders of magnitude larger than the pre-mining conditions, and typical that of a sandy

gravel.

Vertical Hydraulic Anisotropy (KH/KV) of the bedrock = 1. There are no layering in this

geological setting and no indication that either horizontal or vertical fracturing dominates.

Vertical Hydraulic Anisotropy (KH/KV) of the backfilled opencast = 1, as no post mining

layering is anticipated.

The effective porosity value was taken as 0.01. This value was assumed similar to the

specific yield.

Longitudinal dispersion was taken as 50 metres, which is about 10% of expected plume

dimensions, as recommended in various modelling guidelines.

Transverse and vertical dispersion was taken as 5 metres and 0.5 metre respectively.

Stream conductance = 0.01. A value close to the expected aquifer hydraulic conductivity

has been assumed as starting value.

29 http://www.dwaf.gov.za/hydrology



Table 18: Calculated aquifer parameters

Borehole Average T (m2/d) Borehole Depth (metres) Hydraulic Conductivity (m/d) Specific Yield (Sy) Storativity(Ss)

VOL17 4 80 0.038 3.30E-03 1.60E-04

VOL19 39 70 0.442 5.84E-03 1.60E-04

VOL 20 32 70 0.367 3.28E-03 1.00E-07

VOL21 4 170 0.019 3.91E-03 1.60E-04

VOL22 (6 l/s) 65 100 0.521 1.46E-02 1.60E-04

VOL22 (10 l/s) 65 100 0.521 1.64E-02 1.60E-04

AVERAGE T 42 0.318 7.90E-03 1.33E-04

Table 19: Allocated aquifer parameters

Layer Layer Thickness (m) Hydraulic Conductivity (m/d) Transmissivity (m2/d)

Layer 1 50 0.400 20

Layer 2 50 0.200 10

Layer 3 50 0.200 10

Layer 4 50 0.100 5

Layer 5 50 0.100 5

Average/Total Layer 1-3 = 0.267 40



Figure 15: Boundaries of the Numerical Model



Figure 16: Lateral Delineation of the Modelled Area



Figure 17: Lateral Delineation in the Mining Area



9.3 MODEL RUNS

Model simulations were performed to assess the likely hydrogeological impact that the proposed

Volspruit Pit might have on the environment. The hydrogeological impacts are dicussed in section

10 below. The typical stages that will be considered in this section are:

Operational Phase: This phase will be the groundwater conditions expected during the

mining of the proposed Volspruit Pit.

Post-mining Phase: This phase relates to the steady-state conditions following closure of

the opencast. It is assumed for the purpose of this study that the opencast mine will be

backfilled, rehabilitated to pre-mining elevations and allowed to flood.

9.4 LIMITATIONS OF THE MODELLING EXERCISE:

The modelling was done within the limitations of the scope of work of this study and the amount of

monitoring data available. Although all efforts have been made to base the model on sound

assumptions and it has been calibrated to observed data, the results obtained from this exercise

should be considered in accordance with the assumptions made. The assumption that a fractured

aquifer will behave as a homogeneous porous medium can especially lead to error. However, on a

large enough scale (bigger than the REF [Representative Elemental Volume]) this assumption should

hold reasonably well.



10 HYDROGEOLOGICAL IMPACTS AND PUMPING REQUIREMENTS

It is the aim of this chapter to assess the likely hydrogeological impact that the proposed mining of

the Volspruit opencast might have on the environment, including an estimation of the likely

volumes of water that might be necessary to pump in order to dewater the pit.

The model as described above was used to estimate the impact of the proposed Volspruit mining on

the groundwater levels in the area, as well as the likely required pumping volumes. The dewatering

was simulated in Modflow using drains with a hydraulic conductance of 0.001 m2/day. This value

was found through experimentation with this model to be a good compromise between lowering the

groundwater to the desired level and retaining numerical stability.

Following discussions with mine design engineering staff, the liFe of mine was estimated at 15

years, and a progressive drawdown over this period to final depth on mine was assumed. Two

scenarios were modelled, namely the north-eastern shallow section of northern pit, as well as the

deeper south-western section of the same pit.

10.1 OPERATIONAL PHASE

The operational phase of the proposed mine is likely to have an impact on both groundwater

quantity and quality. The open pit itself is not likely to pose a significant threat to groundwater

quality during mining due to the flow gradient towards the pit. However, the associated activities

such as ore processing, tailings dams etc. (mention in section 8.1) may have an impact on

groundwater quality. As the impact of these activities are not part of the scope of work, they will

have to be quantified during the EIA phase when the mine design is complete. The impact on

groundwater quantity will therefore be discussed in this section.

10.1.1 The entire northern pit

It is evident that the preferred mining option would be to mine the whole northern opencast as a

single unit, and preference was thus given to this scenario in the modelling as well.

According to the geological reports received, this opencast is subdivided in two general mining

areas, namely a north-eastern and south-western section. These areas are divided by a fault that

displaced the south-western section vertically downwards for about 100 metres. As a result, the ore

depth in the north-eastern section is about 50 metres below surface, while that of the south-

western section is at 150 metres.

For the purpose of the model, a constant lowering of the mining level of 10 metres per year was

assumed. At the shallower north-eastern section, the groundwater was only lowered to 50 metres

below surface, while the south-western section was further dewatered to the final mining level.

The actual mining plan could deviate substantially from this, but the trends in groundwater

drawdown are not inferred to be that different from those illustrated and discussed below.



Figure 18: Predicted Groundwater Drawdown in Year 5



Figure 21: Predicted Groundwater Levels in Year 15



It follows from these figures that:

The cone of groundwater depression will gradually expand from the mining area in all

directions. It is predicted that this depression will reach the river in about three to five

years.

Depending on the decrease of the mining level with time, the groundwater level will

eventually be well below the river elevation. In ten years it could be as much as 50 metres

below the river and in fifteen years this could increase to 70 metres.

In its natural state, the Nyl River seems to be a gaining river over the potential affected

section; thus the natural inflow to the river could decrease proportionally.

Furthermore, should the bottom sediments of the river be relative permeable, water could

even be drained from the river to the subsurface, further decreasing the flow of the river.

It is advised that a competent hydrologist be appointed to investigate the nature of the

river sediments in this area, and advice on the possible connectivity between the river and

the groundwater.

It is also evident that some of the current used boreholes could experience a lowering of

groundwater level, and associated with this also a decrease in yield. These boreholes

include VOLS1,VOLS3, VOLS4 located on Volspruit 326 KP Portion 2 as well as borehole

ABDUL located on Rondeboschje 295 KR. The borehole GV8 Zoetveld 294 KR may also be

impacted on by the lowering of the water table.

It is also possible to calculate the pumping rate to dewater the aquifer to the required depth of

mining by investigating the flow out from the drains in the numerical model, as tabled below.

Table 20: Predicted volumes of water to be pumped (entire pit)

Pumping Volume Year 3 Year 5 Year 7 Year 9 Year 11 Year 13 Year 15

m3/day 6 000 10 000 10 000 10 000 10 000 11 000 12 000

Ml/month 180 300 300 300 300 330 350

Litre/sec 70 100 100 100 100 130 140

It must again be stressed that actual pump rates could differ considerably from this as different

geological layers with varying hydraulic conductivities are uncovered with depth, as can be

expected given the inhomogeneous fractured nature of the subsurface.

10.1.2 North-eastern shallower pit

From the results in the previous paragraph it is apparent that the likelihood exists that the Nyl

River could be negatively influenced by mining of the northern opencast. An alternative might be to

mine only the north-eastern section of this opencast, where the ore is reported to be situated at a

relative shallow depth of about 50 metres below surface. This section is also further removed from

the Nyl River and less likely to influence the flow in the river. For comparative purposes, the



progressive lowering of the groundwater table was kept at 10 metres per year, thus limiting the life

of mine to five years.

The results of this modelled scenario are depicted in Figure 22 to Figure 24 below. It is evident

these results that the impact on the river is indeed significantly less. It is only in the final year of

mining that the cone of depression is expected to reach the river, and the groundwater lowering at

the river is predicted to be in the order of five metres only.

In this scenario the potential impact on the river is thus expected to be minimal, although the

mining quantities will also be substantially reduced by the smaller area to be mined.

Table 21: Predicted volumes of water to be pumped (north eastern shallower pit)

Pumping Volume Year 2 Year 3 Year 4 Year 5

m3/day 2 000 3 000 4 000 5 000

Ml/month 60 90 120 150

Litre/sec 20 30 50 60



Figure 24: Predicted Groundwater Levels in Year 5



10.1.3 Potential mitigations (GROUNDWATER QUANTITY)

10.1.3.1 Hydraulically isolation of the entire pit

As the results of the model for the entire northern mine indicated that a significant influence on

the Nyl River is to be expected, possible mitigation was considered. The only obvious measure that

came to the fore at this stage of the investigation was to isolate the mining area hydraulically from

the surrounding aquifer. In practice this could be achieved by grouting the bedrock surrounding the

opencast. The engineering feasibility and details for achieving the required low conductivity have

not been considered for this study; rather, the focus has been on the theoretical results of such a

measure.

The concept of horizontal flow barriers is illustrated in Figure 25 and Figure 26 as an east-west

cross section through the main section of the deep part of the mine, before mining and at the end

of mining. The blank areas depict cells that went dry in the modelling process, and should not be

confused with mine pit boundaries.

Similar the first scenario, a constant lowering of the mining level of 10 metres per year was

assumed. Again in the shallower north-eastern section, the groundwater was only lowered to 50

metres below surface, while the south-western section was further dewatered to the final mining

level.

The results of this modelling investigation are depicted in Figure 27 to Figure 29 below. Compared

with the results of the model for the entire pit as showed in Figure 18 to Figure 20, the drawdown

is significantly reduced, although the groundwater level is still predicted to be below the bed

elevation of the river, even as much as 40 metres in places. On inspection of the model, it was

found that groundwater flow in this case is mainly through the unsealed bottom of the pit, as can

be expected. Due to the lower conductivity assumed for the bottom layers, the impact and inflow

is definitely reduced, but could not be completely prevented.

It is thus concluded that, while isolating the pit hydraulically could improve the impact of the

groundwater drawdown in the pit significantly, it might not be enough to prevent an impact on the

flow of the river.

It must again be stressed that actual pump rates could differ considerably from this as different

geological layers with varying hydraulic conductivities are uncovered with depth, as can be

expected given the inhomogeneous fractured nature of the subsurface.

10.1.3.2 Other potential mitigation measures

Should an impact on private groundwater or surface water users occur then the water user should

be compensated by providing an alternative water supplying.

The Nyl river could be diverted around the mine by means of a water pipeline. Furthermore, the

flow in the river may be maintained by allowing the mine to pump water back in the Nyl River

downstream of its workings. The water being discharged should be treated if it does not conform to



Department of Water Affairs standards. The legal and environmental risks should however be

assessed before any such project is undertaken.

10.2 POST MINING PHASE

Following the completion of mining and rehabilitation of the opencast, groundwater will tend to

return to previous levels. However, due to the high hydraulic conductivity of the backfilled

opencast, a new equilibrium position will be attained. The following possible impacts were

considered at the post mining stage:

Following closure of the opencast, the groundwater level will rise to an equilibrium that

could differ from the pre-mining level due to the disturbance of the bedrock and increase

in recharge from rainfall.

Groundwater within the mined areas is expected to deteriorate due to chemical

interactions between the exposed sulphide minerals and the groundwater. The resulting

groundwater pollution plume will commence with downstream movement. No comment can

be made on the tailings dams, waste rock dumps etc., however they are deemed to be

potential sources of contamination post closure. The impact of these sources can be

quantified once the mine design is available.

These impacts are discussed separately below and the significance of each impact is discussed.

10.2.1 Groundwater Quantity

After closure, the water table will rise in the rehabilitated pit to reinstate equilibrium with the

surrounding groundwater systems. However, the mined areas will have a large hydraulic

conductive compared to the pre-mining situation. This will result in a relative flattening of the

groundwater table over the extent of the rehabilitated opencast, in contrast to the gradient that

existed previously.

The end result of this will be a permanent lowering of the groundwater level in the higher

topographical area and a rise in lower lying areas. Intuitively, it would be expected that this raise

in groundwater could result in decanting of the opencast. However, inspection of the predicted

groundwater levels indicates that decanting would probably not occur, as the rise is less than the

current depth to the groundwater level.

10.2.2 Groundwater Quality (opencast related)

Once the normal groundwater flow conditions have been re-instated, polluted water can migrate

away from the rehabilitated opencast. In the absence of large scale extraction, groundwater flow

will be towards the opencast from higher lying areas, and away from the pit towards the river.

Currently groundwater is extracted in the area for crop irrigation, but future land use is

unpredictable. Thus, no extraction has been assumed as worst case scenario.

As the overburden has been shown to be potentially acid generating (see paragraph 5.6.1 above),

this outflow will most likely be contaminated as a result of acid or neutral mine drainage. As

sulphate is normally a significant solute in such drainage, it has been modelled as a conservative



(non-reacting) indicator of mine drainage pollution. A starting concentration of 1 000 mg/litre has

been assumed as a possible scenario, based on past experience in the Bushveld Complex mining

areas.

The migration of contaminated water from the mining area has been modelled as described, and

the results are presented in Figure 30 to Figure 33 in terms of the extent of the pollution plume 10,

20 and 30 after the mine has been closed; and 80 years after closure if only the north-eastern

section is mined. Experience has shown that the plume stagnates after about 80 years, and no

further movement after such time is expected.

Within the limitations of the abovementioned assumptions, it can be estimated from these figures

that:

Movement of the plume will be downstream towards the Nyl River to the west of the

opencast, as can be expected.

Despite the high hydraulic conductivity of the aquifer, the movement of the plume is

predicted to be relatively slower than expected, due to the flat topography (assuming no

groundwater abstraction).

However, after thirty years the front will have moved the distance of about 200 metres to

the river and could start impacting on the water quality. .

If only the north-eastern section is mined, even after eighty years the plume will have

moved only halfway to the river, as depicted in Figure 33 (assuming no groundwater

abstraction). At this stage the plume is predicted to become stagnant as some chemical

reaction will inevitably occur, thereby retarding and absorbing chemical substances in

solution.

The only boreholes which are likely to be affected by pollution are found on Volspruit

Portion 1. However if private boreholes located on adjacent properties to the mine are

pumped, they may become affected on the long term (especially borehole ABDUL)

As stated previously, the results must be viewed with caution as a homogeneous aquifer has been

assumed, while the aquifer is known to be heterogeneous. Furthermore, no chemical interaction of

the sulphate with the minerals in the surrounding bedrock has been assumed. As there must be

some interaction and retardation of the plume, it is hoped that this prediction will represent a

worst-case scenario.



Figure 25: Cross section of hydraulic barriers before mining



Figure 26: Cross section of hydraulic barriers at end of mining



Figure 30: Plume migration full northern opencast after 10 years



Figure 33: Plume migration north-eastern section after 80 years



10.2.3 Groundwater Management

Although no decanting is predicted, there will be a rise in groundwater levels in the lower sections

of the opencasts that could result in decanting if not managed well. Thus, some measures are

needed to mitigate this effect. Reduction of the recharge is recommended and would entail capping

the backfill of the opencast with an impermeable layer, and is encouraged if clayey material is

available.

The recharge into the rehabilitated opencast is a very important variable in solute transport, and

thus the rate of movement of the pollution originating from the pit. A higher recharge will lead to a

faster spread of the pollution plume, and vice versa. Rehabilitation measures must therefore be

directed to decrease recharge into the opencast.

As more groundwater contamination is expected during this stage, it is even more important that

groundwater quality be monitored regularly during this stage, at least on a quarterly basis. This is

essential to provide a reliable database to facilitate eventual closure of the mining operation. The

sampling methods and recommended substances to be sampled for, is briefly described below.

Water samples must be taken from all the monitoring boreholes by using approved sampling

techniques and adhering to recognised sampling procedures. Samples should be analysed for both

organic as well as inorganic pollutants, as mining activity often lead to hydrocarbon spills in the

form of diesel and oil. At least the following water quality parameters should be analysed for:

Major ions (Ca, K, Mg, Na, SO4, NO3, Cl, F)

pH

Electrical Conductivity (EC),

Total Petroleum Hydrocarbons (TPH)

Total Alkalinity

These results should be recorded on a data sheet. It is proposed that the data should be entered

into an appropriate computer database and reported to the Department of Water Affairs.

In conclusion, the following measures are recommended:

All mined areas should be flooded as soon as possible to bar oxygen from reacting with

remaining sulphides.

The final backfilled opencast topography should be engineered such that runoff is directed

away from the opencast areas.

The final layer (just below the topsoil cover) should be as clayey as possible and compacted

if feasible, to reduce recharge to the opencasts.

Quarterly groundwater sampling must be done to establish a database of plume movement

trends, to aid eventual mine closure. A competent hydrogeologist should review the

monitoring data to identify spatial and temporal contaminant trends.

A groundwater monitoring network should be designed once the mine design has been

completed. The network should comply with the requirements of an ISO 14000 monitoring



system. The boreholes indentified during the hydrocensus as well as the newly drilled

boreholes can be used to in the network.



11 CONCLUSIONS AND RECOMMENDATIONS

This section will briefly summarise the findings of this report.

The project area is located in one of the uncharacteristically highly fractured parts of the Bushveld

Complex Northern Limb. The faults in the project area act as conduits and are associated with

large volumes of groundwater as substantiated by the hydrocensus and borehole drilling on the

faults. The top 50m of the rock profile defined by weathering and fracturing is characterised by

intergranular and fracture flow. Groundwater flow and storage is likely occurs in the fractures and

matrix. As the weathering decreases with depth, fracturing becomes dominant over weathering.

Flow and storage of groundwater therefore occurs in fractures in the rock mass.

Groundwater is intensively used for pivot irrigation, potable water and livestock watering. Large

volumes of water are abstracted from the aquifer for irrigation purposes especially on the farms

Volspruit and Bokpoort. The large scale groundwater abstraction may stress the aquifer especially if

more groundwater is being abstracted than what is recharged to the aquifer. The boreholes

indentified during the hydrocensus around the proposed mine show an average yield of 6.5 l/s. The

yields experienced in the Volspruit area are significantly higher than expected for that particular

area. The water levels ranged from 1.5 to 38 mbgl, and averaged at 17.3 mbgl. The groundwater

level does not emulate the topography especially on the farm Volspruit, possibly indicating a

stressed as well as a highly transmissive aquifer. The water levels at the western part of Volspruit

Portion 1 near the river are shallower than the water levels further away. The groundwater flow

direction appeared to be toward the east (away from the Nyl river) at the time of the investigation.

The geophysical survey on the farm Volspruit confirmed the presence of various vertical or sub-

vertical faults. Boreholes were drilled on these faults, with first water strikes varying between 5

and 25 meters. The pump tests conducted on the newly drilled boreholes indicated transmissive

aquifer conditions (average T of 42 m2/d), not only associated with the faults, but with deeply

weathered/fractured areas as well. The groundwater recharge of the area was estimated as 3.2% of

the rainfall (20 mm/a).

Acid-base accounting indicated the potential for the rock to produce acid and consequently acid

rock drainage (ARD). However the rocks do have a neutralisation potential. The sulphides

associated with the ore deposit may not oxidise readily, which could minimise ARD formation.

Metallurgical analyses of the sulphides should verify whether the rocks are potentially acid forming.

The groundwater quality of almost all samples were fair as they contained constituent

concentrations that exceed the SANS 241 maximum allowable standard for domestic use.

Constituents found in concentrations that exceed the standard include magnesium, nitrate and

chloride. Elevated nitrate levels were detected in VOL17, VOL19, VOL20, VOL21 and VOL22 and it is

primarily a health concern in that it can be readily converted in the gastrointestinal tract to nitrite

as a result of bacterial reduction. Nitrate (NO3) found in most sampled boreholes is most likely



sourced from fertilizers. The elevated Cl concentrations may be attributed to induced salinity of

the groundwater from irrigation practices.

The aquifer is reasonably sensitive to contamination and care should be taken with any activities

that could generate pollutants. The aquifer system in the study area is classified as a major

aquifer; where a high level (no or little degradation of groundwater quality) of protection is needed

to adhere to DWA’s water quality objectives.

The Nyl River and alluvial sediments are likely to be hydraulically connected to the weathered and

fractured aquifer. This could however not be substantiated by the waters geochemical signatures

due the recent rainfall at the time of sampling. Although different aquifers units are likely to be

found, they are inferred to be hydraulically connected with each other. It can said that the aquifers

are likely to be recharged by rainfall and the Nyl River. The main receptors in the area are

boreholes on neighbouring properties and the nearby Nyl River system.

The following conclusions were made from the numerical modelling:

The predicted volume of water to be pumped from the pit ranges from 6000 m3/day at year

3 to 12000 m3/day at year 15. These volumes must be refined once the mine design is

complete to accommodate for changes in annual mining depths.

The cone of groundwater depression will gradually expand from the mining area in all

directions. It is predicted that this depression will reach the river in about three to five

years.

Depending on the decrease of the mining level with time, the groundwater level will

eventually be well below the river elevation. In ten years (from start of mining) it could be

as much as 50 metres below the river and in fifteen years this could increase to 70 metres.

In its natural state, the Nyl River seems to be a gaining river over the potential affected

section; thus the natural inflow to the river could decrease proportionally.

Furthermore, should the bottom sediments of the river be relative permeable, water could

even be drained from the river to the subsurface, further decreasing the flow of the river.

It is advised that a competent hydrologist be appointed to investigate the nature of the

river sediments in this area, and advice on the possible connectivity between the river and

the groundwater.

It is also evident that some of the current used boreholes could experience a lowering of

groundwater level, and associated with this also a decrease in yield. These boreholes

include VOLS1,VOLS3, VOLS4 located on Volspruit 326 KP Portion 2 as well as borehole

ABDUL located on Rondeboschje 295 KR. The borehole GV8 Zoetveld 294 KR may also be

impacted on by the lowering of the water table.

If it was decided only to mine the shallow north eastern section, then the impact of the Nyl

River is considerably reduced. Consequently the dewatering requirements only reach an

estimated maximum of 5000 m3/day after 5 years.

While hydraulically isolating the pit (grouting) may reduce the impact on groundwater users, the

Nyl River is still likely to be impacted on. Should an impact on private groundwater or surface



water users occur then the water user should be compensated by providing an alternative water

supplying. The Nyl river could be diverted around the mine by means of a water pipeline.

Furthermore, the flow in the river may be maintained by allowing the mine to pump water back in

the Nyl River downstream of its workings. The water being discharged should be treated if it does

not conform to Department of Water Affairs standards. The legal and environmental risks should

however be assessed before any such project is undertaken.

Inspection of the predicted groundwater levels indicates that decanting would probably not occur,

as the rise is less than the current depth to the groundwater level. The following deduction can be

made from the post closure contaminant plume movement from the pit:

Movement of the plume will be downstream towards the Nyl River to the west of the

opencast, as can be expected.

Despite the high hydraulic conductivity of the aquifer, the movement of the plume is

predicted to be relatively slower than expected, due to the flat topography (assuming no

groundwater abstraction).

However, after thirty years the front will have moved the distance of about 200 metres to

the river and could start impacting on the water quality.

If only the north-eastern section is mined, even after eighty years the plume will have

moved only halfway to the river, (assuming no groundwater abstraction). At this stage the

plume is predicted to become stagnant as some chemical reaction will inevitably occur,

thereby retarding and absorbing chemical substances in solution.

The only boreholes which are likely to be affected by pollution are found on Volspruit

Portion 1. However if private boreholes located on adjacent properties to the mine are

pumped, they may become affected on the long term (especially borehole ABDUL)

A groundwater monitoring network should be designed once the mine design has been completed.

The network should comply with the requirements of an ISO 14000 monitoring system. The

boreholes indentified during the hydrocensus as well as the newly drilled boreholes can be used to

in the network. Both groundwater quality and water levels should be monitored. A comprehensive

groundwater management plan should be drafted as part of the EIA phase. It is recommended that

the numerical model and pump requirements be reviewed once the mine design and other

geotechnical studies have been completed.



APPENDIX A: HYDROCENSUS DATA



APPENDIX B: GEOPHYSICAL REPORT



APPENDIX C: BOREHOLE LOGS



APPENDIX D: AQUIFER TEST RESULTS (AQUIFER PARAMETERS)



APPENDIX E: LABORATORY CERTIFICATE OF ANALYSES

GPT GrassValley hydrogeological investigation report ...

Documents

Transcript of GPT GrassValley hydrogeological investigation report ...