This report may be cited as follows - Squarespacestatic1.squarespace.com/static/54f70cebe4b0d3690344a50b/...This report may be cited as follows: Krige W. G. (2015): 'Surface Water

This report may be cited as follows: Krige W. G. (2015): 'Surface Water and Hydrological Environmental Impact Assessment pertaining to the reopening of the New Kleinfontein's Holfontein Shaft, Ekurhuleni Metropolitan Municipality, Gauteng Province, Republic of South Africa'. Revision 02, Report no. AED0325/2015, African Environmental Development.

Cover main photo: The concrete slab covering the Holfontein Shaft, with the "hill" of the Holfontein Hazardous Waste Landfill Site in the distance on the horizon. This is where the Holfontein Stream, flowing past the shaft, begins. (Photo: Garfield Krige 03/03/2015)

Prepared for:

Prepared by:

Prime Resources (Pty) Ltd PO Box 2316, Parklands, 2121 The Workshop 70 7th Avenue, Parktown North, Johannesburg, 2193 Tel: +27 11 447 4888 Email: [email protected]

African Environmental Development PO Box 1588, Rant-en-Dal, 1751 129 Malmani Rd, Sterkfontein Country Estates, Krugersdorp, 1750 Tel: +27 83 657 0560 Fax: +27 86 670 5102 Email: [email protected]

Prepared on behalf of:

New Kleinfontein Goldmine (Proprietary) Limited http://www.gold1.co.za

African Environmental Development No 129 Malmani Road Sterkfontein Country Estates Krugersdorp

African Environmental Development PO Box 1588

Rant-en-Dal 1751 Tel: - 083 657 0560 Fax:- 086 670 5102

E-mail: - [email protected] http://www.aed.co.za

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Table of Contents:

EXECUTIVE SUMMARY ............................................................................... IV

DECLARATION OF INDEPENDENCE ......................................................... IX

INTRODUCTION AND BACKGROUND: ........................................................ 1

1. DESCRIPTION OF THE CATCHMENT, SURFACE WATER FLOW

PATTERNS AND WATER QUANTITIES ................................................. 4

1.1 DESCRIPTION OF THE CATCHMENT ........................................................ 4

1.1.1 Holfontein Stream, Blesbokspruit and Suikerbosrant River ........ 4

1.1.2 Vaal and Orange Rivers ............................................................. 5

1.2 THE AVERAGE FLOW IN THE STREAMS AT THE STUDY AREA .................. 11

1.2.1 Holfontein Stream ....................... Error! Bookmark not defined.

1.3 SURFACE WATER FLOW PATTERNS AT THE HOLFONTEIN STUDY AREA ... 16

1.4 AVERAGE FLOW QUANTITIES OFF THE HOLFONTEIN STUDY AREA .......... 19

1.5 RAINFALL AND EVAPORATION AT THE HOLFONTEIN STUDY AREA ............ 19

1.5.1 Rainfall ..................................................................................... 20

1.5.2 Evaporation .............................................................................. 23

1.6 PROJECTED PEAK FLOW QUANTITIES .................................................. 25

1.6.1 Determination of run-off volumes from a 50-year flood falling

over the Holfontein study area .................................................. 26

1.6.2 100-Year Flood Lines for the Holfontein Stream at the Holfontein

Study Area ................................................................................ 29

1.6.2.1 Background to Flood Lines: .................................................. 29

1.6.2.2 Legal Considerations: ........................................................... 30

1.6.2.3 Flood Line Modelling ............................................................. 31

1.6.2.4 Results: ................................................................................. 32

1.6.2.5 Expected flood peaks in the Holfontein Stream and the impact

of the additional discharge from the Holfontein Shaft ............ 34





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1.6.2.6 The effect of the additional 7 Ml/day mine water on the

average flow in the Holfontein Stream .................................. 36

1.7 HOLFONTEIN SHAFT WATER BALANCE ................................................. 38

1.7.1 Inflow into Holfontein Mine ....................................................... 38

1.7.2 Water leaving the Holfontein Mine ............................................ 39

1.7.3 Mine water discharge options ................................................... 43

2. SURFACE WATER QUALITY ................................................................ 48

2.1 SURFACE WATER MONITORING ............................................................ 48

2.1.1 Description of the sampling points ............................................ 49

2.1.1.1 Sample Holfontein 1 .............................................................. 49




2.2 DISCUSSION OF THE WATER QUALITY ................................................... 54

1.2.1 General discussion of the surface water quality at the study area

................................................................................................. 55

2.3 AN INTERPRETATION OF THE SAMPLES AT THE HOLFONTEIN STUDY AREA,

USING HYDROCHEMICAL IMAGING ........................................................ 58

3. THE WATER QUALITY IN THE HOLFONTEIN SHAFT ........................ 61

4. DRAINAGE DENSITY OF THE HOLFONTEIN STREAM ...................... 62

5. DOWNSTREAM WATER USE ............................................................... 63

6. SURFACE WATER MONITORING PROGRAMME ............................... 66

7. ENVIRONMENTAL IMPACT ASSESSMENT ........................................ 67

7.1 SURFACE HYDROLOGY OF THE HOLFONTEIN STREAM ........................... 68

7.1.1 100-Year Flood Lines and mine surface infrastructure ............. 68

7.1.2 Mining within the 100-year flood lines ....................................... 68

7.1.3 The impact on the average base flow in the Holfontein Stream

from groundwater discharged from the Holfontein Shaft .......... 69





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7.1.4 The impact on the peak flow volumes in the Holfontein Stream

should Holfontein Shaft water be discharged into this stream .. 70

7.1.5 The impact of the groundwater discharged from the Holfontein

Shaft on the water users at Welgedacht Smallholdings ............ 71

7.1.6 The impact of the haul road crossing on the flow regime of the

Blesbokspruit ............................................................................ 71

7.1.7 The ability of the Holfontein Mine to separate "clean" and "dirty"

water during a 50-year/24-hour flood event .............................. 74

7.2 SURFACE WATER QUALITY OF THE HOLFONTEIN STREAM...................... 76

7.2.1 The impact of mining at Holfontein Shaft on the water quality in

the Holfontein Stream ............................................................... 76

7.2.2 The impact of the discharge of groundwater from the Holfontein

Shaft on the water quality in the Holfontein Stream .................. 76

7.3 ENVIRONMENTAL IMPACTS DURING THE CONSTRUCTION, OPERATION AND

DECOMMISSIONING PHASES OF THE HOLFONTEIN PROJECT................... 78

7.3.1 Construction/Recommissioning Phase ..................................... 78

7.3.2 Operational Phase .................................................................... 79

7.3.3 Decommissioning ..................................................................... 81

7.4 QUANTITATIVE RISK ASSESSMENT ....................................................... 81

8. CONCLUSIONS ..................................................................................... 90

9. REFERENCES ....................................................................................... 91

APPENDIX 1: HOLFONTEIN STREAM AND BLESBOKSPRUIT FLOOD

LINES CAD FILES ........................................................................................ 93

APPENDIX 2: WATER QUALITY ANALYSES REPORT ............................. 93





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Executive Summary New Kleinfontein Goldmine (Pty) Ltd (NKGM) wishes to reopen an old gold mining shaft in the East Rand named the Holfontein Shaft, which was originally established by the Holfontein (TCL) Gold Mining Company Limited in the 1930's. This shaft was operational during the 1930's and early 1940's and has been abandoned for about 75 years. Currently the shaft, which has a shaft depth of approximately (~) 315 m, is flooded to an elevation of 112 m below surface. The purpose of the Holfontein Project is to supplement the drop in production once the New Kleinfontein Goldmine Modder East (ME) Operations production begins to decline. Prime Resources (Pty) Ltd, the lead environmental agent for the re-opening of the Holfontein Shaft project, appointed African Environmental Development (AED) to conduct a study on the surface water hydrology and hydrochemistry and to establish the environmental impacts the re-opening of the shaft may have on the surface water associated with the shaft. This report is the product of this study. The study concluded the following:

The Holfontein Shaft locates in quaternary catchment C21D, which has a mean annual precipitation (rainfall) of 697.98 mm. However, the average annual actual rainfall at the Holfontein Shaft of 685 mm/a is slightly less than the quaternary catchment's average annual rainfall (of 697.98 mm/a). This catchment falls in the Upper Vaal Water Management Area. An unnamed stream (called the Holfontein Stream for the purposes of this document) flows past the Holfontein Shaft and all surface water drainage from the shaft area would drain towards this stream.

The average annual A-Class Pan evaporation at the Holfontein Shaft is

2 140 mm/a.

During a theoretical storm with a radius of 5 Km and a return period of 50-years, falling over the Holfontein study area, a total volume of 1 699 633 m³ would run off a surface area of natural grassveld of 78.5 Km² in Veld Zone 4 (Grasslands of Interior Plateau), over the entire 24-hour period. This equates to a surface run-off of 21.7 l/m² from natural grassland. This value was amended to reflect the true surface run-off that would flow from known surfaces encountered in a mining environment. It was determined that the holding capacity of the pollution control dam (PCD) would be adequate to contain all surface





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run-off from potentially contaminated surfaces at the Holfontein Mine during a 50-year/24-hour storm event.

Four samples were collected; three from the Holfontein Stream and

one from the Blesbokspruit where the proposed new haul road would pass over the Blesbokspruit. The water in the Holfontein Stream is of a good quality, in spite of the proximity of the Holfontein Hazardous Waste Landfill site locating in the upper reaches of the stream's catchment. Likewise the water quality of the water currently in the flooded mineshaft is of a good quality. However, it is expected that this water quality would deteriorate once dewatering of the shaft begins.

The shaft is currently flooded. Depth profiling and sampling by Shango

Solutions (Handley, 2014) indicated that the water level in the shaft located at an elevation of 112 m below surface. Using the LiDAR-surveyed contour lines acquired from the Ekurhuleni Metropolitan Municipality, it was established that the slab over the shaft is at an elevation of ~1596 m above mean sea level (mamsl). Thus, the water level in the shaft is at 1481 mamsl. The water level in the Blesbokspruit at the same latitude (i.e. where the N12 freeway crosses the Blesbokspruit) is at ~1577 mamsl. This means that the water level in the shaft is well below (~96 m below) the surface water level in the Blesbokspruit and thus also well below the assumed groundwater level in the same region. If any water flow were to occur, it would be from surface or from the perched water table to the Holfontein Mine void environment and not vice versa, i.e. decant to surface is unlikely. This fact is to some extent encouraging and could indicate that infiltration from the overlying dolomitic aquifer into the Holfontein Mine void could occur at a comparatively slow rate (i.e. inflow into underground workings would be slow, and therefore potential for contamination would be comparatively low).

The 100-year flood lines for the Holfontein Stream were modelled and it

was shown that the water level during a flood with a return period of 100 years would not reach the shaft. The embankment, on which the N12 freeway is built, would to a certain extent, lower the flood elevations on the downstream side, i.e. on the side where the Holfontein Shaft locates. The security fence around the Holfontein Shaft is 264 m away from the 100-year flood line; thus, all surface infrastructure locates well outside the 100-year flood lines of the Holfontein Stream. The nearest part of the security fence around the shaft and surface infrastructure area is 368 m from the Holfontein Stream and thus also complies with the 100-m buffer of GN704. Thus, the surface infrastructure area complies in full with the 50- and 100-year flood line limitations part of GN704, i.e. no surface infrastructure will be placed within the 100- or 50-year flood zones, or within 100m from the edge of the Holfontein Stream. Although both the 50- and 100-





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year flood lines must be indicated in terms of GN704 of the National Water Act, and as the 100-year flood lines are 268 m from the shaft, it was not deemed necessary to also model the 50-year flood lines. The 100-year flood lines are always at a higher elevation than the 50-year flood lines. Additionally, in small catchments, such as the catchment of the Holfontein Stream, the 50- and 100-year flood lines plot mere centimetres apart (vertically). Thus, for this small catchment, the 100-year flood lines will be used where GN704 requires the 50-year flood lines.

The point where the proposed haul road will be passing over the

Blesbokspruit is currently in a poor environmental condition. The wetland has simply been filled in, while the bridge over the river consists of a pipe laid in the river channel and then filled up with soil. This is in contravention with the National Water Act as well as the National Environmental Management Act. Although NKGM did not construct the road and therefore they are not responsible for what was done there, NKGM will be using this road for several years as their haul road, linking the Holfontein Shaft to the NKGM ME Operations plant. For this reason the 10-year flood lines were modelled for this reach of the Blesbokspruit. A flood with a return period of 10 years was chosen on an economical basis, given the limited lifespan of the mine. It is far cheaper to repair a culvert every 10 or 20 years than constructing a bridge for a 100-year flood, particularly at a road with limited or no use after mining ceases. A downstream railway line crossing will form a "dam" behind this bridge during a 10-year flood. Due to the bridge backwater, the 10-year flood lines are particularly wide apart at the haul road crossing. However, for the same reason the velocity of flowing water at the crossing is comparatively low during a storm with a return period of 10 years. It is AED's contention that NKGM must improve the flow of water under the road across the wetland by installing smaller culverts at regular intervals, rather than a pipe at a single point, which will promote channel formation. This issue will have to be addressed in the Mine's WULA.

Due to the non-perennial nature of the Holfontein Stream, there are no

actual users of water from the stream. However, some of the smallholdings in close proximity to the Holfontein Stream in Welgedacht Smallholdings (Welgedacht SH) may be impacted by a larger flow when dewatering of the Holfontein Shaft commences. The culverts under the two roads, Carnation and Phlox Roads, were never designed to accommodate more than the base flow in the Holfontein Stream. It is AED's contention that, if NKGM is to discharge groundwater directly into the Holfontein Stream, NKGM must upgrade these culverts to accommodate the additional flow that would result from mining at Holfontein. It must be further kept in mind that the proposed haul route from the Holfontein Shaft to the NKGM will make





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use of Carnation Road. It would be counterproductive if the trucks could not reach the gold plant due to flooding of the bridges. In general, flooding at the Welgedacht SH would be exasperated by the very low gradient and the high water level in the receiving body of water, the Blesbokspruit. From Carnation Rd to Phlox Rd, the Holfontein Stream falls from 1578 to 1575 m, i.e. a 3-m fall over stream a distance of 795 m. Thus the slope in this reach of the stream is a mere 0.003773 m/m (a fall of 1:265), an exceedingly low fall. Furthermore, although the stream falls by ~1 metre at the culvert under Phlox Rd, the remaining 920 m of the canal from the Phlox Rd culvert to the end of the canal in the Blesbokspruit remains at the same elevation, i.e. 1574 mamsl, the elevation of the water surface in the Blesbokspruit at this confluence (Refer to Photo 7). Thus, it could be expected that all the riparian smallholdings alongside the Holfontein Stream, but particularly those downstream of the Phlox Rd culvert, would regularly be inundated with floodwaters during the wet season (irrespective of whether mine water is discharged into the Holfontein Stream). Referring to Figure 18, it can be seen that four of the six smallholdings downgradient of the Phlox Rd culvert are not occupied and the two that are occupied (plots 34 and 35) in Poppy Rd, the residences are built right on the road, i.e. as far as possible from the stream. Also refer to the 100-yr flood lines of the Blesbokspruit, shown as dark red lines in Figure 18, in this area. An increase in base flow in the Holfontein Stream would compound the flooding at these 6 plots, particularly during flooding events. However, the study has also shown in Section 1.5.2.5 (Graph 7 and Table 11) that the difference in flood elevation for all the return periods, with the additional 7 Ml/day discharged from the Holfontein Shaft, will be negligibly small.

Although the flow in the Holfontein Stream, after including the flow of

mine water from the Holfontein Shaft, will not have a significant effect on the flood elevations of the peak flow rates that could be expected in the Holfontein Stream due to storms with return periods ranging between 1 and 20 years, the additional 7 Ml/day that is expected to be pumped from the mine workings will make a significant difference to the base flow in this stream. The additional water will change the character of the Holfontein Stream from being a non-perennial stream to being a perennial stream for the duration of mining. Furthermore, and given that it is expected that DWS will enforce a high water quality for the water discharged into the Holfontein Stream in the mine's WUL, both the water quality (depending on the requirements of the WUL) in the water pumped from underground and the perennial nature of the stream may have a detrimental effect on the aquatic vegetation within the stream and its riparian zone. It is expected that reeds and bulrushes will proliferate and that this proliferation of aquatic vegetation could lead to the impeding of flow in this stream, particularly at the inlets to culverts where roads cross the stream. Should discharge occur





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into the Holfontein Stream, it is recommended that NKGM implement a maintenance programme where the vegetation growth is monitored and when it becomes excessive, particularly at the culverts, that steps be taken to clear the inlets of the culverts.

In addition to discharging the mine water into the Holfontein Stream at

the Holfontein Shaft, three alternative points for mine water discharge were evaluated, using water quality and hydrology as indices. It was concluded that discharging the mine water directly into the Blesbokspruit at a point opposite the Municipal Waste Water Treatment Plant (WWTP) would be the best environmental option overall.

Areas of Concern

Flooding in Welgedacht SH due to the increase in flow in the Holfontein Stream resulting from the possible discharge of mine water from the Holfontein Shaft. This goes hand in hand with the establishment of more prolific aquatic plants that could impede the flow of floodwaters and cause increased flood elevations.

The condition of the haul road bridge over the Blesbokspruit and

sections of road passing through the Blesbokspruit wetland. In its present state, it is expected that this part of the haul road will be flooded for significant parts of the rainy season, making it impassable for the trucks transporting the ore and waste rock. Additionally, the crossing is at present encouraging channel formation in a wetland where channels are not to be encouraged. By upgrading the river and wetland crossing and by spreading the culverts across the width of the wetland, while using smaller culverts in the centre of the stream ensuring that channel formation is minimised, channel formation can be controlled.

Due to its poor location, its proximity to the Blesbokspruit and given the

generally low topography of the land surrounding it, the area occupied by the Welgedacht SH is prone to regular flooding. This is an area of concern, particularly if the Holfontein Mine intends discharging additional water into the Holfontein Stream. In order to establish potential liability for flood damage, it is recommended that regular monitoring or inspections are conducted at the Welgedacht SH area during, or shortly after any large rainstorm. Photographic records must be collected after each flooding event. It is recommended that the flood lines presented in this report are made available to residents to inform them of the location of their properties in relation to flood lines.





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Declaration of Independence

The independent Environmental Assessment Practitioner

I, declare that I:

act as an independent Environmental Practitioner in this study of the surface water and

hydrological aspects pertaining to the surface water aspects relating to the re-opening of the

Holfontein Shaft Project;

do not have and will not have any financial interest in the undertaking of the activity, other than

remuneration for work performed in terms of the Environmental Impact Assessment Regulations,

2010;

have no and will have any vested interest in the proposed activity proceeding;

have no, and will not engage in, conflicting interests in the undertaking of the activity;

undertake to disclose, to the competent authority, any material information that have or may

have the potential to influence the decision of the competent authority or the objectivity of any

report, plan or document required in terms of the Environmental Impact Assessment

Regulations, 2010;

will ensure that information containing all relevant facts in respect of the application is distributed

or made available to interested and affected parties and the public and that participation by

interested and affected parties is facilitated in such a manner that all interested and affected

parties will be provided with a reasonable opportunity to participate and to provide comments on

documents that are produced to support the application;

will ensure that the comments of all interested and affected parties are considered and recorded

in reports that are submitted to the competent authority in respect of the application, provided

that comments that are made by interested and affected parties in respect of a final report that

will be submitted to the competent authority may be attached to the report without further

amendment to the report;

Signature of the Environmental Assessment Practitioner: African Environmental Development

Name of Company: 4 August 2015

Date:

Garfield Krige. Pr.Sci.Nat. Aquatic Science (Reg. No. 400068/10)





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Surface Water and Hydrological Environmental Impact Assessment pertaining to the reopening of the Holfontein Shaft by New Kleinfontein Goldmine (Pty) Ltd Ekurhuleni

Metropolitan Municipality, Gauteng Province, South Africa

Introduction and Background: The Holfontein Shaft locates immediately south of the N12 Freeway immediately east of the turn-off to the road linking Etwatwa with the town of Springs, named Pansy Road where it passes through the Welgedacht SH. The mineshaft locates on the Remaining Extent (RE) of the Farm Holfontein 71 IR. From the Gold One International Ltd (hereafter, Gold One) website, http://www.gold1.co.za, and other sources, the following information was obtained for Holfontein: Holfontein underground reserves span 2 181 Ha and is located adjacent to and due east of Modder East in the East Rand of South Africa's Gauteng Province. Of this 2 181 Ha, an area of 126 Ha will actually be mined. The original Holfontein mine began with the Holfontein (TCL) Gold Mining Company, a subsidiary of the Transvaal Consolidated Lands & Exploration Company, which was started on the Holfontein farm. It is unclear exactly when mining at Holfontein began but a share issue on 26 January 1937 gives some indication of its vintage. At some point in time a shaft was sunk in the southeastern sector of the farm and a small amount of development was carried out on the Main Reef. The purpose of the Holfontein Project is to supplement the drop in production once the New Kleinfontein Goldmine [Modder East (ME) operations] tonnage profile begins to decline. The intended initial focus at Holfontein is that of the Main Reef remnants located above the water level of the Eastern Basin Mile Void. The drill-indicated Upper Leader Reef (located 3 metres to 30 metres above the Main Reef), in the northeastern quadrant of the Modder East prospect, is an additional focus. The life of mine (LoM) will consist of two years of construction and development (2019-2020), and 8 years of gold production (2021-2028). A further 6 months to a year is assumed for decommissioning and closure. All waste rock and ore will be transported from the Holfontein Project to the ME Operations plant by road using conventional 30 tonne road trucks. Thus, there will not be any waste rock or ore stockpiles at Holfontein.






Prime Resources (Pty) Ltd, the lead environmental agent for this project, appointed African Environmental Development cc (hereafter, AED) to conduct a study on the surface water issues associated with the reopening of the old Holfontein Shaft, and to present a report describing the Environmental Impacts the reopening of this shaft may have on the surface water and hydrological environment. The currently flooded Holfontein Shaft is located in the Ekurhuleni Metropolitan Municipality in the Gauteng Province. There is a small stream flowing roughly from northeast to southwest towards the Blesbokspruit. This stream rises at the Holfontein Hazardous Waste Landfill Site, passing the Holfontein Shaft to the north and northwest of the shaft and flowing through the Welgedacht Smallholdings downstream from the Holfontein Shaft to its confluence with the Blesbokspruit, almost due east of the ME Metallurgical Plant. There is a planned haul road route on which the ore and waste rock will be transported by truck from the Holfontein Shaft to the ME Metallurgical Plant. This road (an existing road) passes over the Blesbokspruit at an existing makeshift bridge, i.e. a pipe placed in the main channel of the watercourse with earth filling over the wetland and pipe.

Photo 1: The existing makeshift bridge (a 1-m pipe under the road) and existing road through the wetland, where the proposed haul road will be crossing the Blesbokspruit

The Holfontein Shaft is currently flooded, and according to NKGM, is not linked hydraulically to the main mining void of the Eastern Mine Void Basin. Therefore, mining can take place at this shaft without having to pump the volumes that used to be pumped at Grootvlei Mine (60 to 120 Ml/day).






According to the project description, a maximum estimate of 7 Ml/day would have to be pumped from the shaft at the peak of mining. From a geological perspective, the Holfontein Shaft locates on the Vryheid Formation of the Ecca Group, Karoo Supergroup. A comparatively thin layer of the Dwyka Group, Karoo Supergroup, underlies the Vryheid Formation. In this area, the Karoo Supergroup was deposited directly on the dolomite rock of the Malmani Subgroup, Chuniespoort Group, Transvaal Supergroup. The surface outcrop of the contact of the Karoo Supergroup with the Transvaal Supergroup underlying it, is a mere 1.7 Km to the southwest of the Holfontein Shaft and, as the gold-bearing Witwatersrand Supergroup rocks are older than the Transvaal Supergroup rocks (i.e. the Witwatersrand rocks will underlie the Transvaal Supergroup rocks), it is very likely that the shaft would have been sunk through the dolomite. Furthermore, elevation of the Holfontein Shaft is a mere 10 m above the contact between the Karoo and Transvaal Supergroups. It is therefore likely that dolomite would have been intersected within a very short depth below surface when the shaft was originally sunk. Thus, and given the limitations to pumping equipment in the heydays of gold mining, the fact that mining is the 1930s-1940s was at all possible, indicates that major water strikes were not intersected in the part of the shaft through the dolomite. Apparently, mining at Holfontein was not stopped due to excessive water ingress into the shaft. Although not in the same order of magnitude as the water volumes that were pumped from the Grootvlei Mine, the estimated peak water volume of 7 Ml/day will be discharged to surface water resources, possibly into the small, unnamed stream (named for the purposes of this document, the "Holfontein Stream"). For this reason this stream formed an integral part of this surface water study. Additionally, the Holfontein Stream passes in close proximity to the Holfontein Shaft and thus, the 100-year flood lines were modelled to ensure that no mining activities occur within these flood lines. As described above, the proposed haul road will pass over the Blesbokspruit to the ME Operations. The current makeshift bridge will not be suitable to transport heavily laden trucks and a new bridge will have to be constructed (or the current river crossing would have to be upgraded). The 50- and 100-year flood lines were modelled. However, as the total LoM at Holfontein would be in the order of ~10 years, an additional flood line produced by a storm with a return period of 10 years was also modelled to determine the sizing of the culverts that will have to be used to support the roadway across the Blesbokspruit wetland. It is considered common (acceptable) practice to use the life of the structure or project (in this case 10 years) for design purposes.






1. Description of the Catchment, Surface Water Flow Patterns and Water Quantities

1.1 Description of the Catchment

The study area includes the Holfontein Shaft area, the small stream (Holfontein Stream) flowing past the shaft area and the Blesbokspruit where the proposed haul road crosses this river. The primary river draining this region is the Vaal River, which flows from its origin along the continental watershed near Breyten towards its confluence with the Orange River near the town of Douglas. A small, non-perennial stream, the Holfontein Stream, flows past the Holfontein Shaft. This stream originates at the Holfontein Hazardous Waste Landfill Site and, after flowing through the Welgedacht Smallholdings, flows into the Blesbokspruit (refer to Figures 1, 3 and 4).

1.1.1 Holfontein Stream, Blesbokspruit and Suikerbosrant River

The Blesbokspruit flows in a generally southerly direction from its origin on the farm Vlakfontein 25 IR, through Etwatwa and adjacent residential areas, past the New Kleinfontein and Grootvlei Gold Mines, along the eastern side of Springs, through the Marievale Bird Sanctuary, and past Nigel, where the broad wetland ends and where the river begins flowing in a well-defined river channel. South of Nigel, the Blesbokspruit makes a 90º right-hand bend to the west and when it reaches the southwestern corner of Nigel, it makes a 45º left-hand bend, after which it continues in a generally southwesterly direction up to its confluence with the Suikerbosrant River. The Suikerbosrant River flows into the Vaal River downstream from the Vaal Dam. The confluence of the Suikerbosrant River with the Vaal River occurs within the upper reaches of the Vaal Barrage Dam. The Holfontein study area locates in quaternary catchment C21D (refer to Figure 1), within the Upper Vaal River Water Management Area. The upper reaches of the Blesbokspruit drain this quaternary catchment. It then continues through quaternary catchments C21E and C21F until reaching its confluence with the Suikerbosrant River. Quaternary catchment C21D has a mean annual rainfall of 697.98 mm but part of this catchment includes areas with slightly higher rainfall values. Referring to Figure 8, Section 1.4.1, the 1' x 1' (1 minute x 1 minute - Lat/Lon, not time) tile, within which the Holfontein Shaft lies, has an average rainfall of 685 mm, which is about 13 mm lower than the average rainfall for the entire quaternary catchment, C11J (of 697.98 mm). The mean annual run-






off for this catchment, i.e. the rainfall in millimetres that actually reaches the surface streams as surface run-off, is 36.1 mm/a (Midgley et. al. 1994), (Middleton & Bailey 2005).

1.1.2 Vaal and Orange Rivers

Vaal River The Vaal River has its source at continental watershed separating the Komati River catchment from the Vaal River catchment. While the Komati River flows into the Indian Ocean in Moçambique, the Vaal River flows via the Orange River into the Atlantic Ocean. The origins of both these primary rivers are close to the town of Breyten. The first major dam in the path of the Vaal River is the Grootdraai Dam. On its way to its confluence with the Orange River, the Vaal River then flows through the Vaal Dam, the Vaal Barrage Dam (alias Loch Vaal), the Bloemhof Dam, the Vaalharts Dam and the Douglas Dam/weir. The Vaal River then flows into the Orange River, immediately downstream from Douglas. The Vaal River is probably the single most important river in South Africa as it supplies water to the largest part of the people and industries of South Africa. Its flow is augmented with inter-basin transfers, among others, from the Tugela River basin, from the Usutu River basin and from the Orange (Senqu) River basin in Lesotho. Orange River The Orange River, also known as the Oranjerivier (Afrikaans), Gariep River (Nama) and Senqu River (Lesotho), flows westwards and empties into the Atlantic Ocean. It is the longest river in South Africa and rises in the Drakensberg and Maluti Mountains of Lesotho a mere 193 Km west of the Indian Ocean. In spite of its proximity to the Indian Ocean, it flows westwards across virtually the entire South Africa to the Atlantic Ocean, where it empties its load into the Atlantic Ocean at Alexander Bay. With a catchment basin of 973 000 Km² (about 77% of the surface area of South Africa) and total length of ~2 200 Km, the Orange River is not only the longest river, but also the river with the largest catchment in South Africa. The quaternary catchment, rivers/streams and other relevant information discussed above are shown in Figures 1 to 3 and Figure 5.





NKGM Reopening of Holfontein shaft - Surface Water EIA final Page 6

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Figure 1: The location of the Holfontein Shaft study area on a map showing the regional quaternary catchments.

Also shown are the boundaries of the Water Management Areas (indicated as red lines - “C” referring to the Water Management Area of the Vaal River, "A", to the Crocodile (west) and Marico Rivers, and "B" indicating the Olifants River WMA).






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Figure 2: The Holfontein Shaft in relation to the Water Management Areas (WMAs), the primary rivers and some of the more important dams within the Vaal River catchment






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Figure 3: The study area showing the actual Holfontein and its associated Ventilation Shafts and infrastructure footprint areas, the proposed haul road, the ME Operations, as well as the surface water sampling points. This image was produced using the LiDAR-surveyed data obtained from the Ekurhuleni Metropolitan Municipality






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Figure 4: The study area showing details regarding the layout of the Holfontein Shaft and its associated Ventilation Shaft






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Figure 5: The general topography surrounding the study area at Holfontein, showing the secondary river, the Blesbokspruit and its tributary, the Holfontein Stream draining the study area. This image was produced using the 5-m contour lines obtained from the Chief Directorate Surveys and Mapping (Surveyor General)






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1.2 The Average Flow in the Streams at the Study Area

1.2.1 Holfontein Stream

There are no flow-gauging stations in the Holfontein Stream. It was thus necessary to find a stream in the same region, with a similarly sized catchment and which does have records of flow and then to use the data from this stream to derive the flow patterns in the Holfontein Stream. Unfortunately (and unsurprisingly) there is no such a stream in the DWS database, which is in close proximity to the Holfontein site. Although there are records for the flow in the Blesbokspruit within the same quaternary catchment, the gauging station is near Nigel, hardly representative of the non-perennial nature of the flow in the Holfontein Stream. It was thus necessary to find another stream in the same general geographic region with similar characteristics to those of the Holfontein Stream. Such a stream with almost identical characteristics does actually exist, albeit, ~83 Km west of the Holfontein Stream. In spite of the distance, both streams are tributaries of the Vaal River and both catchments begin right at the continental watershed. The catchments are also virtually the same size. Furthermore, both catchments locate at almost the same latitude. This stream is the Middelvleispruit, draining quaternary catchment C23D, and there is a DWS flow gauging station (Station No C2H026) where it flows off the rocks of the Witwatersrand Supergroup and on to the dewatered dolomitic aquifer of the Gemsbokfontein compartment. This is probably the only reason that there was a DWS gauging station in such a small stream (Refer Figure 6). The catchment of the Middelvleispruit of 28.777 Km² is slightly larger than that of the Holfontein Stream (of 25.227 Km²), but this difference in surface area is offset by the slightly lower mean annual run-off (MAR) of the Middelvleispruit catchment (MAR of 29.5 mm for the Middelvleispruit vs. MAR of 36.1 mm for the Holfontein Stream). Thus, as far as these statistics go, the pattern of flow (seasonal graph) in the Holfontein Stream would likely be very similar to the pattern of flow in the Middelvleispruit. We acquired the flow data for the Middelvleispruit from DWS, produced a curve of the average flow over the time span the data covers (1957 to Nov 1996), and then derived an equation that fits the graph. This equation was then adapted to produce a new graph of the Holfontein Stream that matches the calculated flow in the Holfontein Stream but retaining the flow characteristics of the Middelvleispruit. The flow in the Holfontein Stream was calculated using the surface area and MAR of quaternary catchment C21D, within which the Holfontein Stream locates.






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Figure 6: The DWS flow gauging station in the Middelvleispruit and its catchment of 28.777 Km² in relation with the Holfontein Stream catchment of 25.227 Km². Although the catchments are ~83 Km apart, both catchments form part of the Vaal River catchment and both catchments begin right at the continental watershed

The flow records in Table 1 show the flow in the Middelvleispruit, recorded by the DWS at gauging station, C2H026 for the period it was operational. The average monthly-recorded flow in the Middelvleispruit can be presented as a graph, shown in Graph 1.






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Hydrological

YearOct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct

Total for

Year

1957/1958 0.022 0.063 0.026 0.045 0.029 0.076 0.073 0.057 0.056 0.049 0.038 0.101 0.022 0.635

1958/1959 0.025 0.048 0.020 0.020 0.016 0.031 0.029 0.036 0.039 0.021 0.014 0.012 0.025 0.311

1959/1960 0.011 0.032 0.017 0.039 0.022 0.015 0.017 0.017 0.015 0.014 0.014 0.011 0.011 0.224

1960/1961 0.012 0.024 0.010 0.010 0.024 0.023 0.034 0.037 0.029 0.023 0.019 0.015 0.012 0.260

1961/1962 0.010 0.042 0.052 0.013 0.012 0.010 0.029 0.013 0.013 0.010 0.010 0.008 0.010 0.222

1962/1963 0.070 0.021 0.006 0.013 0.005 0.008 0.008 0.006 0.010 0.010 0.003 0.003 0.070 0.163

1963/1964 0.006 0.006 0.010 0.003 0.003 0.000 0.000 0.003 0.006 0.000 0.000 0.000 0.006 0.037

1964/1965 0.023 0.025 0.031 0.038 0.040 0.045 0.035 0.029 0.025 0.019 0.016 0.014 0.023 0.341

1965/1966 0.024 0.024 0.031 0.039 0.042 0.046 0.035 0.029 0.025 0.019 0.016 0.012 0.024 0.341

1966/1967 0.025 0.025 0.033 0.041 0.044 0.048 0.037 0.030 0.024 0.019 0.016 0.012 0.025 0.351

1967/1968 0.026 0.025 0.034 0.041 0.046 0.050 0.038 0.031 0.025 0.019 0.016 0.013 0.026 0.365

1968/1969 0.027 0.026 0.036 0.044 0.048 0.052 0.040 0.001 0.002 0.002 0.001 0.000 0.027 0.279

1969/1970 0.001 0.004 0.012 0.002 0.006 0.000 0.000 0.001 0.002 0.003 0.003 0.000 0.001 0.034

1970/1971 0.000 0.000 0.000 0.001 0.000 0.000 0.001 0.009 0.016 0.005 0.002 0.000 0.000 0.034

1971/1972 0.000 0.000 0.000 0.020 0.000 0.007 0.000 0.000 0.007 0.016 0.004 0.000 0.000 0.054

1972/1973 0.000 0.004 0.001 0.000 0.000 0.000 0.001 0.000 0.000 0.001 0.001 0.000 0.000 0.008

1973/1974 0.011 0.005 0.000 0.009 0.001 0.003 0.005 0.001 0.001 0.001 0.000 0.000 0.011 0.037

1974/1975 0.000 0.010 0.011 0.023 0.055 0.043 0.057 0.045 0.068 0.033 0.025 0.012 0.000 0.382

1975/1976 0.005 0.061 0.054 0.132 0.108 0.122 0.131 0.195 0.092 0.076 0.052 0.054 0.005 1.082

1976/1977 0.193 0.093 0.044 0.079 0.113 0.259 0.126 0.095 0.068 0.067 0.067 0.042 0.193 1.246

1977/1978 0.050 0.071 0.140 0.397 0.446 0.404 0.227 0.153 0.118 0.097 0.045 0.011 0.050 2.159

1978/1979 0.043 0.044 0.051 0.044 0.033 0.011 0.008 0.026 0.027 0.031 0.034 0.025 0.043 0.377

1979/1980 0.086 0.110 0.015 0.033 0.084 0.084 0.057 0.018 0.031 0.028 0.021 0.027 0.086 0.594

1980/1981 0.040 0.021 0.044 0.034 0.056 0.142 0.060 0.039 0.039 0.018 0.035 0.037 0.040 0.565

1981/1982 0.079 0.068 0.124 0.124 0.053 0.016 0.024 0.015 0.015 0.013 0.010 0.008 0.079 0.549

1982/1983 0.004 0.007 0.000 0.000 0.000 0.000 0.001 0.001 0.001 0.001 0.001 0.001 0.004 0.017

1983/1984 0.003 0.004 0.012 0.015 0.004 0.002 0.004 0.006 0.010 0.012 0.008 0.002 0.003 0.082

1984/1985 0.007 0.017 0.006 0.004 0.001 0.001 0.000 0.004 0.004 0.004 0.004 0.003 0.007 0.055

1985/1986 0.010 0.007 0.015 0.015 0.035 0.008 0.055 0.006 0.009 0.007 0.005 0.000 0.010 0.172

1986/1987 0.005 0.012 0.270 0.117 0.021 0.044 0.020 0.019 0.021 0.022 0.025 0.039 0.005 0.615

1987/1988 0.029 0.021 0.020 0.015 0.012 0.026 0.026 0.016 0.014 0.012 0.006 0.012 0.029 0.209

1988/1989 0.007 0.013 0.003 0.009 0.024 0.016 0.018 0.017 0.022 0.011 0.010 0.002 0.007 0.152

1989/1990 0.001 0.016 0.009 0.019 0.019 0.025 0.038 0.041 0.029 0.022 0.013 0.008 0.001 0.240

1990/1991 0.002 0.001 0.005 0.012 0.012 0.031 0.017 0.012 0.013 0.012 0.011 0.012 0.002 0.140

1991/1992 0.014 0.004 0.006 0.005 0.000 0.000 0.001 0.003 0.008 0.004 0.007 0.003 0.014 0.055

1992/1993 0.002 0.010 0.008 0.002 0.011 0.008 0.004 0.004 0.004 0.001 0.000 0.000 0.002 0.054

1993/1994 0.044 0.004 0.035 0.012 0.024 0.015 0.016 0.012 0.008 0.005 0.001 0.000 0.044 0.176

1994/1995 0.000 0.002 0.000 0.000 0.000 0.000 0.000 0.002 0.002 0.002 0.002 0.000 0.000 0.010

1995/1996 0.001 0.003 0.013 0.027 0.147 0.109 0.118 0.083 0.046 0.019 0.047 0.025 0.001 0.638

Average: 0.025 0.026 0.032 0.039 0.038 0.045 0.034 0.028 0.025 0.020 0.015 0.014 0.025 0.341

Table 1: The flow in the Middelvleispruit at Gauging Station C2H026 in Million m³ (Mm³), for the period 1957-1995 (when the flow meter was stolen). The exceptionally high flow records of the 1995-1996 year was ignored, as from this time onwards, a sewage pump station in Randfontein in the upper reaches of this stream began overflowing, discharging large amounts of raw sewage into the stream and distorting the flow records. The author can confirm that this pump station is still overflowing (June 2015)

From Graph 1 and Table 1 it can be seen that the flow in the Middelvleispruit is highly seasonal, reaching a high peak during January, with almost no flow from the end of May to the beginning of October.






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Average Monthly Flow: Middelvleispruit (1957 to 1995)

y = -2E-06x5 + 9E-05x4 - 0.0014x3 + 0.0078x2 - 0.0128x + 0.0306

0.010

0.015

0.020

0.025

0.030

0.035

0.040

0.045

0.050

Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct

Month

Flo

w (

Mil

lio

n m

³/m

on

th)

Graph 1: The monthly flow trend of the Middelvleispruit at Gauging Station C2H026

As stated above, an equation was derived from Graph 1 and this equation was adapted to produce Graph 2, which is representative of the flow in the Holfontein Stream. However, when comparing the average annual run-off measured in the Middelvleispruit at Gauging Station C2H026 with the calculated annual surface run-off from this catchment using the WR2005 surface run off of 29.5 mm, it is clear that the measured values and the calculated values do not match (refer to Table 2). The gauged annual run-off from the Middelvleispruit catchment is 0.341 Million m³/a, while the calculated run-off is 0.849 Million m³/a. This is a significant difference and could likely be attributed to the fact that this catchment lies right in the upper reaches of the quaternary catchment and that the run-off here is not necessarily representative of the overall surface run-off off the entire quaternary catchment. Whatever the reason, we had to introduce a constant (multiplication factor) in the formula. Thus, to compensate and reduce the calculated flow in the Holfontein Stream by the same margin as was calculated for the Middelvleispruit, a reduction factor was calculated, as shown in Table 2.






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Catchment: 28.77749 Km²

Catchment: 28777490 m²

MAR 29.5 mm/a

Volume MAR in a year: 848936 m³

Gauged MAR in a year: 0.8489 Million m³/a

Volume MAR in a year: 0.3411 Million m³/a

Run-off Reduction Factor: 0.4018

Catchment: 25.22697 Km²

Catchment: 25226970 m²

MAR 36.1 mm/a

Volume MAR in a year: 910693.6 m³

Volume MAR in a year: 0.9107 Million m³/a

Applying Reduction Factor: 0.366 Million m³/a

Middelvleispruit

Holfontein Stream

Table 2: The statistics for the two catchments, which were used to derive the reduction factor that was used in the subsequent calculations of the derived surface run-off for the Holfontein Stream

Graph 2 thus shows the likely seasonal flow pattern in the Holfontein Stream. This is the best presentation of this river's flow that can be modelled, without having an actual flow gauging station in the stream.

Average Derived Monthly Flow: Holfontein Stream

y = -2E-06x5 + 9E-05x4 - 0.0015x3 + 0.0083x2 - 0.0137x + 0.0329

0.010

0.015

0.020

0.025

0.030

0.035

0.040

0.045

0.050


Month

Flo

w (

Mil

lio

n m

³/m

on

th)

Graph 2: The inferred monthly flow pattern of the Holfontein Stream, using the actual flow patterns of the Middelvleispruit and the reduction factor shown in Table 2






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The calculated monthly flow in the Holfontein Stream (in Million m³), as plotted in Graph 2 is shown in Table 3 below:

MonthTheoretical

Run-off

Actual Run-off (After

applying reduction

factor)

Oct 0.066 0.026

Nov 0.070 0.028

Dec 0.085 0.034

Jan 0.105 0.042

Feb 0.102 0.041

Mar 0.119 0.048

Apr 0.091 0.036

May 0.076 0.030

Jun 0.066 0.027

Jul 0.052 0.021

Aug 0.041 0.016

Sep 0.037 0.015

Oct 0.066 0.026

Totals: 0.911 Mil m³ 0.366 Mil m³

Table 3: The calculated monthly flow (in Million m³) in the Holfontein Stream, based on the flow trend of the Middelvleispruit, as measured at gauging station, C2H026 (Table 1). Please note that October is shown at the beginning and end of the table (as well as in Table 1 and Graphs 1 and 2). This is not an error. It is done to close the loop of the graph and to produce a more representative equation for the graph. The second October value is not included in the total cubic metres

1.3 Surface Water Flow Patterns at the Holfontein Study Area

As described in Section 1.1, the study area falls in quaternary catchment C21D. As can be seen from Figures 3 and 4, the only river of importance near the study area is the Holfontein Stream, draining the entire study area. Surface drainage from the study area occurs northwards towards the embankment of the N12 Freeway and then westwards along the embankment towards the Holfontein Stream. There is a slight possibility that water falling in the eastern part of the shaft yard would drain eastwards to small tributary of the Holfontein Stream. However, after flowing under the N12 Freeway embankment, this tributary joins the Holfontein Stream immediately to the north of the road, so that this water ends up in the Holfontein Stream as well. Figure 7 was created to demonstrate the actual direction of flow in the vicinity of the Holfontein study area. It must be borne in mind that both Figures 7 and 8 illustrate surface water flow across the shaft areas, as recorded before mining activities re-commence, to enable the correct placement of berms/cut-off trenches, once mining commences. The actual flow rates and quantities flowing off contaminated surfaces will be discussed in Section 1.5.1. Likewise, the management of "clean" and "dirty" water will be discussed in this section.






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Figure 7: The direction of surface water flow across Holfontein shaft study area

From Figure 7, it is clear that the flow patterns around the Holfontein Shaft area are rather simple. Virtually all the surface flow originating within the main shaft area will drain northwards, directly towards the embankment of the N12 freeway, which will then deflect the flow westwards into the Holfontein Stream. A small fraction of surface drainage off the site may flow eastwards to the tributary, passing east of the study area, as indicated by the orange shading in Figure 7. However, this will be a minute volume of water (hardly visible in Figure 7) and a berm or cut-off trench will easily direct this water towards the northwestern side of the site, i.e. to the pollution control dam (PCD). Judging by the red and orange shadings in Figure 7 north of the Ventilation shaft, the natural drainage off this area will be towards the north-northeast, i.e. towards the Holfontein Tributary. However, it is unlikely that any polluting material would be used at the ventilation shaft and thus, it would not be necessary to contain/treat surface run-off from this surface. The topography of a drainage area not only shows which direction surface drainage would flow, but also dictates the volumes and speed/momentum (~energy) at which water would flow off a particular piece of land. In other words, if water runs off a very flat






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area, the amount of water flowing off this area should theoretically be less in terms of the receiving body of water than for example, water running off a very steep terrain, as more time would be available for recharge of groundwater and for evaporation, etc. Water flowing off the flat area would also contain less energy, i.e. erosion would occur at a slower rate, but more importantly, the water would have more time to infiltrate into the ground through the surface and would also not have sufficient energy and turbulence to hold heavier sediment in suspension. For this reason we also produced Figure 8. In Figure 8, we show the slope of the land in degrees rather than the direction of flow as shown in Figure 7. This will provide an indication of the energy that surface run off would contain and will also provide an indication of the time that run-off water would spend on the surface while flowing off the land. This, in turn, will control the rate of erosion, the evaporation loss, the infiltration rate into the ground, and the rate and particle size of the solids that could theoretically be held in suspension by the flowing water.

Figure 8: The slope of the land in the vicinity of study area. This diagram shows that the slope of the land where the rivers flow, in the vicinity of the study area, is very low, i.e. the stream basins are comparatively flat






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Figure 8 shows that the slope of the land at and around the study area is not very steep. The actual working surface at the mineshaft is constructed on a flat apron and once proper drainage channels are constructed, efficient drainage of this area should be relatively simple.

1.4 Average Flow Quantities off the Holfontein Study Area

The rainfall in quaternary catchment C21D is 697.98 mm of which 36.1 mm (MAR) reaches surface watercourses annually as surface run-off (Midgley et. al. 1994) (Middleton & Bailey, 2005). The total area occupied by the proposed surface infrastructure (as shown in Figure 3 - the white rectangle around the shaft) is approximately 4.43 Ha. The area within the security fence at the vent shaft will cover an additional 1.68 Ha. Using the mean annual run-off (MAR), it can be calculated that the proposed mining infrastructure, with the combined surface area as estimated above, would intercept some 1 919 m³ surface run-off to the Holfontein Stream annually (about 5.26 m³/day). This amount of water is negligible when viewed in context of the catchment of the Vaal River (the Holfontein Stream's receiving body of water). Most of these surfaces will be classified as contaminated areas and this water would have to be contained in the PCD. However, the value calculated above is somewhat useless, as it is well known that in South Africa, surface run-off does not occur evenly throughout the year, but rather seasonally and in the form of (mostly) thunderstorms. For this reason it was necessary to also base the average surface run-off on monthly rainfall data for this area. Refer to Section 1.5 for the peak flow quantities that could be expected at the Holfontein Shaft. The rainfall records, originally recorded in the 2007 EMP for ME, as recorded in an earlier surface water EIA report for NKGM (Krige, 2012), were used, as these records produced a total rainfall very close to what is reported by WR2005 (Middleton & Bailey, 2005) for the 1'x 1' tile within which the existing Holfontein Shaft locates. Refer to Figure 9 for detail of the rainfall, based on the 1' x 1' (one minute x one minute) “tile”. According to this drawing, the 1' x 1' tile within which the Holfontein Shaft locates receives 685 mm rainfall per annum, while WR2005 records an annual rainfall of 697.98 mm for the entire quaternary catchment. These values are very similar.

1.5 Rainfall and Evaporation at the Holfontein Study Area

Both rainfall and evaporation records are available for the ME Operations (Krige, 2012). It was therefore not necessary to access the DWS National database to acquire this data. The nearest meteorological station of DWS which has reliable data, is in any case significantly further away from the Holfontein Shaft than the ME Operations.






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1.5.1 Rainfall

Table 4 shows the average monthly rainfall for the NKGM area. These values were derived from the EMP for NKGM and tally well with the values reported by the Water Resources of South Africa WR2005 (Middleton & Bailey, 2005). Also refer to Figure 9 for a minute-x-minute (1’x1’ – Lat/Lon not time) representation of the rainfall in the vicinity of NKGM. Figure 9 uses the data from the WR2005 study as it is presently the best available in South Africa. The rainfall for NKGM is shown in Table 1 (NKGM EMP, 2007).

Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Total

7 22 56 107 125 115 110 89 37 26 7 8 709

Table 4: The rainfall for NKGM (NKGM EMP, 2007)

The average monthly rainfall records were used to create a graph and to obtain a curve for that graph, as shown in Graph 3.

Rainfall at New Kleinfontein GM

y = 0.0011x6 - 0.0476x5 + 0.7623x4 - 4.6831x3 + 0.6948x2 + 67.049x - 6.6643

0

20

40

60

80

100

120

140


Month

Rain

fall

(m

m)

Graph 3: The average seasonal trend of rainfall at NKGM

A trend line was added which is represented by the equation: y = 0.0011x

6 - 0.0476x

5 + 0.7623x

4 - 4.6831x

3 + 0.6948x

2 + 67.049x - 6.6643

In terms of Table 4, the mean annual precipitation is 709 mm. These values tally closely with the WR2005 data shown in Figure 9, which records a rainfall






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over the two minute “squares” over which NKGM falls of about 706.5 mm/a. The 2007 EMP records it as 709 mm/a, a negligible difference. According to Figure 9, the mean annual precipitation (MAP) at the Holfontein Shaft should be 685 mm/a. This is slightly less than the rainfall at the NKGM (24 mm less). It was thus necessary to adapt the formula representing the rainfall curve in Graph 3 and to produce a new graph which tallies with the rainfall in the 1' x 1' tile in Figure 9.

Figure 9: A more accurate and more site-specific Mean Annual Precipitation (MAP) map for the areas surrounding the Holfontein study area, shown on a 1-minute x 1-minute grid (Data: WR2005), shows that the MAP of 685 mm/a at the study area is slightly lower than the MAP of 697.98 mm average for quaternary catchment C21D.

For this reason it was necessary to recalculate the rainfall for Holfontein, while retaining the seasonal rainfall patterns shown in Graph 3. The formula representing the curve in Graph 3 was adapted to produce a new formula, which would represent a rainfall curve that would produce a total annual






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rainfall of 685 mm at Holfontein, while retaining the seasonal characteristics of the rainfall curve of the NKGM (Graph 3). The new curve representative of the expected average rainfall patterns at the Holfontein study area, is shown in Graph 4 below:

Calculated Monthly Rainfall at Holfontein Shaft

y = 0.0011x6 - 0.046x5 + 0.7365x4 - 4.5246x3 + 0.6712x2 + 64.779x - 6.4387

0

20

40

60

80

100

120

140


Month

Rain

fall

(m

m)

Graph 4: The re-calculated rainfall curve likely to be representative of the actual rainfall at the Holfontein study area, but still retaining the monthly and seasonal fluctuations recorded at Met Station C1E007

The calculated, monthly rainfall at the Holfontein study area is shown in Table 5 below:

MonthRainfall at

Holfontein Shaft

Oct 54

Nov 103

Dec 121

Jan 111

Feb 106

Mar 86

Apr 36

May 25

Jun 7

Jul 8

Aug 7

Sep 21

Oct 54

Total: 685 Mil m³

Table 5: The average monthly rainfall, which is likely to be received by the Holfontein study area, based on the actual rainfall recorded at NKGM, but recalculated to meet the actual annual rainfall at the Holfontein study area, shown in Figure 9






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1.5.2 Evaporation

Figure 10 shows the mean annual A-Pan Class evaporation rate for the general areas surrounding the Holfontein Study Area. As can be seen from Figure 10, there is an increasing trend in the evaporation rate from east to west across this particular part of the Republic of South Africa. The A-Pan Evaporation at the Holfontein Study Area is ~2 140 mm/a. There is sometimes confusion between the Symons Pan Evaporation (S-Pan) and the American A-Pan Evaporation. For clarity, the conversion between S-Pan and A-Pan Evaporation rate is as follows:

A-Pan = 26.3622 + (1.0768 x S-Pan) S-Pan= − 16.2354 + (0.8793 x A-Pan) Graph 8 shows the A-pan evaporation trend at NKGM. The values used in this graph were derived from the values shown in Table 7.

Month Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep OctTotal for

Year

A-Class Pan

Evaporation (mm) 223.9 220.7 224.0 220.9 206.5 182.4 154.4 130.3 118.0 123.4 148.1 187.6 223.9 2 140.2

Table 6: The monthly average A-Pan evaporation at the Holfontein Shaft

The evaporation in the general vicinity surrounding the Holfontein study area is shown in Figure 10 (WR2005 - Middleton & Bailie, 2005) and Graph 5.

Monthly A-Class Pan Evaporation at Holfontein Shaft

y = -0.0002x6 - 0.0081x5 + 0.4753x4 - 6.2053x3 + 29.215x2 - 54.09x + 254.47

100

120

140

160

180

200

220

240


Month

Evap

ora

tio

n (

mm

)

Graph 5: The average A-Class Pan Evaporation rate at the Holfontein study area






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Figure 10: The average A-Class Pan evaporation rate for the areas surrounding the Holfontein study area (Data: WR2005). In this generalised presentation of the South African evaporation it is obvious that evaporation increases from the east and south coast towards the north and west of the Southern African sub-continent

The actual evaporation lines shown in Figure 10 were used to interpolate the values in-between these lines. This was done to determine the actual evaporation at the Holfontein Shaft study area. These interpolated lines are shown in Figure 11.






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Figure 11: Using the actual evaporation lines shown in Figure 10, these interpolated lines around the Holfontein study area suggests that the Holfontein Shaft should have evaporation of ~2 140 mm/a

1.6 Projected Peak Flow Quantities

It is common knowledge that in South Africa, rainfall does not occur in average amounts throughout the year, but rather on a seasonal basis. In general the South African rainfall can be very erratic and unpredictable on a year-on-year basis, but also from one thunderstorm to the next. One thunderstorm may be relatively small or average and the next one could cause a flood. Then, once in a while a storm will occur which will exceed the rainfall produced by an average storm by several orders of magnitude. For this reason, it is the instruction from the authorities (DWS) that "clean" and "dirty" water must remain separated during storm events with return periods of up to 50 years.






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1.6.1 Determination of run-off volumes from a 50-year flood falling over the Holfontein study area

In terms of GN704 Section 6 (b), (d) and (f), promulgated in terms of the National Water Act of 1998 (Act 36 of 1998), all dams, canals, pollution control dams, etc. must be designed so that spillages do not occur as a result of a 50-year, 24-hour flood event taking place and that water flowing in clean and dirty systems must not mix during this particular storm event. To determine the amount of total surface run-off, a typical design storm with a return period of 50 years, falling over an area of 78.5 Km², was modelled (i.e. a theoretical circularly-shaped design thunderstorm with a 5-Km radius), which more than adequately includes the study area at its centre. The total volume of water produced by this storm that would actually run off from the surface areas on which it falls was then determined. The area modelled is shown in Figure 12.

Figure 12: The zone of rainfall around the study area used to model a storm with a 50-year return period. The circle has a radius of 5 Km representing a surface area of 78.5 Km²






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The results are summarised in Graph 6, below.

Graph 6: The discharge produced by a 50-year storm for the first 500 minutes of a total period of 24 hours. This storm produced a total run-off of 1 699 633 m³ over the entire 24-hour period off a surface area of natural grassveld of 78.5 Km² in Veld Zone 4 (Grasslands of Interior Plateau)

Graph 6 shows that a total surface run off of 1 699 633 m³ would occur over the entire 24-hour period flowing off natural veld in Veld Zone 4 (Grasslands of the Interior Plateau). This equates to 21.7 litres per m². These calculations are assuming natural veld, which will not be the case once mining commences. It was thus necessary to determine the surface areas that would potentially produce polluted run-off and allocate run-off coefficients to each of these surfaces to determine the total volume of run-off that could be expected off a 50-year, 24-hour storm event. These calculations are discussed below. By using the total run-off indicated by the curve in Graph 6 and applying surface run-off coefficients for common surfaces that may be present at mines or industries, the run-off values for the Holfontein Shaft were calculated, shown in Table 7 below.

Surface Type Run-off

Natural Open Grassland (Coefficient C in "Q=CIA" = 0.10) 21.7 l/m² (Graph 6)

Railway Yards 65.0 l/m²

Offices (coverage equiv. to residential areas) 86.6 l/m²

Industrial Area up to 50% covered: 151.56 l/m²

Industrial Area >50% covered: 173.21 l/m²

Streets, Pavements, etc. 173.21 l/m²

Roofs 194.86 l/m²

Open Dams Collection (i.e. no outflow) 216.51 l/m²

Table 7: The different surface run-off values for different surface types normally associated with a mining environment






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Please refer to Figure 4 for a description of each of the surfaces at the Holfontein Shaft. Referring to Figure 4, it should be noted that some of the surfaces, such as offices, covered waiting areas, were excluded from the calculations summarised in Table 8 below, as they did not pose a pollution problem. The discharge from each square metre, running off each of the areas specified above, was used to calculate the total volume running off each of the different surface types at Holfontein during a storm event with a 50-year, 24-hour storm event. It must be noted that these values are specific to the study area, the area within the red circle in Figure 12. These values cannot be applied anywhere else in the country. Using the above run-off values, the following run-off volumes can be expected to either run off, or be collected during a storm with a return period of 50 years falling over the Holfontein shaft surface areas:

Surface Area (m²) Run-Off (m³)

Shaft Apron (incl. Winders, compressors, etc.) 5 831 1 136

Salvage Yard (assuming no surface cover) 2 111 137

Fuel & Lube storage bay 302 52

Shaft 58 9

Explosives Loading area, etc. (Item 13, Fig 4 ) 551 107

Marshalling, Timber & Laydown area 2 907 504

Water Treatment Plant 670 116

PCD 1 203 260

Sewage Plant (in addition to normal sewage) 452 78

Total: 2 400.2

Surface run-off

Table 8: The total volume in m³ that is likely to run off, or be collected in, each of the potentially contaminated surfaces at the Holfontein Shaft

Table 8 shows that the total run-off from the potentially contaminated surfaces at Holfontein Shaft would be 2 400 m³. This included rainwater falling on the PCD as well as on the sewage plant, but not including the actual sewage being treated at the sewage plant. The PCD, numbered Item 9 in Figure 4, has a surface area of 1 600 m² (40 x 40 m). Assuming this dam will have an average usable depth of 3.0 m and assuming an inside wall slope of 1.5:1, the usable volume of the dam would be 3 500 m³, after allowance had been made for a freeboard of 800 mm. Thus the PCD is adequately sized to accommodate the run off from contaminated surfaces during a 50-year, 24-hour storm event. Please note that the values discussed above (run-off in litres per square metre of surface area) are volumes that would actually run off a particular surface and is not the total rainfall falling on that surface. In almost all instances, the






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volume running off any surface will be less than the amount of rain falling on that surface. The only exception is open dam surfaces, where every litre of rainfall falling on the dam surface would actually remain in the dam, provided that the dam already had some water in it at the beginning of the storm.

1.6.2 100-Year Flood Lines for the Holfontein Stream at the Holfontein Study Area

There are two streams of importance associated with the re-opening of the Holfontein Shaft. The first is the Holfontein Stream, which passes in close proximity to the Holfontein Shaft. The second is the Blesbokspruit, at the crossing with the proposed new haul road linking the Holfontein Shaft with the ME metallurgical plant. In terms of Section 144 of the National Water Act of 1998 (Act 36 of 1998), it is required to indicate the 100-year flood lines in the zone affected by the mineshaft and its associated infrastructure. During 2012 the flood lines for the reach of the Blesbokspruit in close proximity to the NKGM were modelled and both the 50- and 100-year flood lines were produced. The area where the proposed haul road crosses over the Blesbokspruit was included in this study. It was subsequently only necessary to model the flood lines of the Holfontein Stream in the vicinity of the Holfontein Shaft. The catchment of the Holfontein Stream is shown in Figure 13. 1.6.2.1 Background to Flood Lines: A 100-year flood is a flood event that has a 1% probability of occurring in any given year. The 100-year flood is also referred to as the 1% flood, since its annual exceedance probability is 1%, or as having a return period of 100-years. The 100-year flood is generally expressed as a flow rate (e.g. m³/s). Based on the expected 100-year flood flow rate in a given stream or river, the flood’s water level can be mapped as an area of inundation. The resulting floodplain map is referred to as the 100-year floodplain, which may be very important in how close to the stream buildings or other activities (including power lines) are allowed. A common misconception exists that a 100-year flood is likely to occur only once in a 100-year period. In fact, statistically, there is an approximate 63.4 % chance of one or more 100-year floods occurring in any given 100-year period. The Probability (Pe) of one or more of a specifically sized flood occurring during any return period, would exceed the specifically sized flood severity, can be expressed as:






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…where Pe is the probability, T is the return period of a given storm (e.g. 100-year, 50-year, 20-year, etc.), and n is the number of years. The exceedance probability Pe is also described as the natural, inherent, or hydraulic risk of failure when, e.g. referring to dams, bridges, etc.). However, the expected value of the number of 100-year floods occurring in any 100-year period is 1. In other words, 100-year floods have a 1% chance of occurring in any given year (Pe = 0.01), 10-year floods have a 10% chance of occurring in any given year (Pe = 0.1), 50-year floods have a 2% chance of occurring in any given year (Pe = 0.02), etc. The percent chance of an x-year flood occurring in a single year can be calculated by dividing 100 by x.

Figure 13: The catchments of the Holfontein Stream

1.6.2.2 Legal Considerations: In terms of Section 144 of the National Water Act of 1998 (Act 36 of 1998), a flood line, representing the highest elevation that would probably be reached during a storm with a return period of 100 years, must be indicated on all plans for the establishment of townships. The term, “establishment of






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townships” includes the subdivision of stands or farm portions in existing townships, if the 100-year flood lines are not already indicated on the plans, or when the land use category of a particular section of land is changed. The purpose of this section of the act is to inform developers/landowners or residents/occupants/tenants of the dangers of flooding. For this reason, insurance companies also insist on knowing where the 100-year flood lines locate at properties they insure, particularly when a property is near a watercourse. Similarly, Government Notice GN704, specifically dealing with the location of mines relative to flood lines, promulgated in terms of the National Water Act of 1998 (Act 36 of 1998), legislates that no residue deposit, dam, reservoir or any of its associated infrastructure may be placed within the 100-year flood lines or within 100 m from a river’s edge, whichever distance is the greatest. It continues that no opencast or underground mine may be located within the 50-year flood line of a stream or river (or within 100 m from the edge of a river, whichever distance is the greatest) and neither may one erect any sanitary convenience, fuel depots, reservoir or depots for any substance which may cause, or is likely to cause, pollution of a water resource within the 50-year flood line of any watercourse. 1.6.2.3 Flood Line Modelling Methodology: The determination of flood lines is done in two steps, 1) modelling a succession of “design storms”, each of them producing a particular discharge in m³/s and, 2) routing the highest discharge produced in step 1 through cross sections across representative sections of the river at the study area, which then assigns an elevation to which the floodwaters would rise at that particular cross section. The flood lines are then drawn using these elevations at the cross sections as guides. The flood lines indicate the area that will be inundated during the 100-year flood event in the river. The first part of the process comprises the modelling of a succession of “design storms” with statistical return periods of 100-years and durations ranging from 1 to 24 hours, falling over the catchment of the study area during a single 100-year return period rainfall event. If a catchment is smaller than approximately 50 Km², design storms are derived using a deterministic approach, as opposed to the purely statistical methods used for larger catchments (i.e. catchments over ~50 Km²). This is done as a result of the difficulty of extrapolating the frequency analyses of peak discharges and experience envelope diagrams for small areas, as the range of enveloped values becomes extremely wide as the catchment area decreases. Another reason is the problem of attempting to assign recurrence intervals to these experience envelopes. Hence, for catchments under ~50






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Km², the conventional procedure is to employ the original Rational Method (Q = CIA), an Empirical Method and the Amended Rational Method, as researched, designed and published in Reports, 1/72, ‘Design Flood Determination in South Africa‘, 1972 and 1/74, ‘A Simple Procedure for Synthesizing Direct Runoff Hydrographs’ 1974, produced by a joint venture between the CSIR and the Hydrological Research Unit (a division of the Department of Civil Engineering at the University of the Witwatersrand). The discharge is then derived using a weighting system that depends on the surface area of the catchment. Due to its catchment being smaller than 50 Km², the Holfontein Stream was modelled using the latter methods. The results of this model are summarised in Table 7 for the 100-year storm falling over the catchment.

0 to 5 Km² 5 to 10 Km² 10 to 18 Km² >18 Km² Calc. Dischrg Weighting Result

5 3 1.5 0.25 118.2 0.25 29.6

4 2 1 0.25 123.6 0.25 30.9

1 3 5 7.00 86.1 7.00 602.8

Weighted Design Discharge: 88.43 m³/s

Weightings for Catchment Areas: Holfontein Stream @ Holfontein Shaft

Normal Rational

Empirical

H.R.U

Method:

Table 9: A discharge of 88.43 m³/s was derived for the 100-year storm falling over the Holfontein Stream catchment, using a weighting system where surface-area-based weights are allocated to the three methods used to determine the run-off off the catchment.

In the second part of the process, the discharge in m³/s, produced by the design storm that produced the highest discharge, is routed through cross sections across the stream within the study area. The flood lines of the Holfontein Stream were plotted as shown in Figure 14, using Mannings formulae for Open Channel Flow and using software developed by AED. In total nine cross-sections were plotted across representative sections of the Holfontein Stream, as shown in Figure 14. Cross Section 4 was plotted at the bridge where the N12 Freeway crosses the Holfontein Stream, while Cross Section 6 was plotted across the Pansy Road Extension to determine the impact of these two bridges on the100-year floodwaters at the Holfontein Shaft. 1.6.2.4 Results: A storm with a return period of 100 years falling over the catchment of the Holfontein Stream will have a time of concentration (TC - the time from the beginning of the storm until the maximum discharged is reached) of just less than 2 hours (1.93 Hours, to be exact). This storm will produce the highest discharge of 88.43 m³/s in the Holfontein Stream at the study area. The elevations containing the maximum discharge, at each cross section along the stream, were then plotted on either side of the stream's centre-line






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and transferred, in plan, to the drawing (Figure 14), to demarcate the 100-year flood lines for the Holfontein Stream. The resulting flood lines are supplied as a separate CAD file, appended to this report (Appendix 1). Although GN704 requires both the 50- and 100-year flood lines, it was decided to only model the 100-year flood line. The reason is that with small catchments of this size, the 50- and 100-year flood lines plot so close together that they often appear as a single line when plotted on an A4 page. Furthermore, the 100-year flood line is always the safer of the two lines and thus it is recommended to use the 100-year flood line even if the 50-year flood lines are specified in certain instances in GN704. To validate our statement, we modelled the 50-year design storm. This storm produced a discharge of 74.07 m³/s, compared to the 88.43 m³/s for the 100-year storm. The 50- and 100-year flood lines will literally plot a few centimetres apart (vertically).

Figure 14: The 100-year flood lines for the reach of the Holfontein Stream where it passes the Holfontein Shaft






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Figure 15: A 3-D model, showing the area of inundation that will result from a flood with a return period of 100 years in the reach of the Holfontein Stream near the Holfontein Shaft. A 3x vertical exaggeration was applied, to increase the sense of depth in this model.

1.6.2.5 Expected flood peaks in the Holfontein Stream and the impact

of the additional discharge from the Holfontein Shaft To determine the flood peaks that would occur during the life of the Holfontein Mine, all the accepted flood return periods were modelled (in addition to the 100-year return period). These peak discharge volumes are shown in Table 10 below:

Return Period

(Year)

Discharge

(m³/s)

2 23.17

5 40.32

10 50.01

20 62.42

50 74.07

100 88.43

Table 10: The expected discharge volumes produced by storms with return periods ranging between 2 and 100 years

The values shown in Table 10 were then converted to a graph. It was found that the graph, with formula: y = 18.781 x ln(x) + 8.136, best fitted the curve produced by the modelled floods. This curve is presented in Graph 7 below:






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Expected Flood Discharge Peaks in the Holfontein Stream

y = 18.781Ln(x) + 8.136

5

10

15

20

25

30

35

40

45

50

55

60

65

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Flood Return Period (Years)

Maxim

um

Exp

ecte

d D

isch

arg

e p

er

Retu

rn

Peri

od

(m

³/s)

Graph 7: The expected flood discharge peaks for storms with return periods ranging between 1 and 20 years, falling over the catchment of the Holfontein Stream.

Note that this graph represents the maximum peak discharge (Y-axis) that could be expected from storms with particular return periods (X-axis). As an example, a storm with a 1-year return period would produce a peak discharge in the Holfontein Stream of about 8 m²/s (on average only once in one year). A storm with a 12-year return period would produce a peak discharge of about 55 m³/s. Alternatively the 12-year example can be written as follows: "It can be expected that, on average, once in every 12 years, there will be a storm, falling over the catchment of the Holfontein Stream, that would produce a peak flow in this stream of 55 m³/s". These peaks are the highest discharges that can be expected to occur during a particular return period. These are not average flows but the highest flood peaks that are predicted to occur during a specific return period. The maximum volume of mine water of 7 Ml/day, as reported in the project description, that would potentially be discharged by the Holfontein Mine, was then added to these values to establish the effect of the additional mine water on the expected peak discharges in this stream. These values and the percentage change (compared to the natural peak discharges in this stream) are shown in Table 11 below:






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Return Period

(Year) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Discharge (m³/s)8.14 21.15 28.77 34.17 38.36 41.79 44.68 47.19 49.40 51.38 53.17 54.81 56.31 57.70 59.00 60.21 61.35 62.42 63.44 64.40

Discharge (incl

7Ml/d Mine water)

(m³/s) 8.22 21.24 28.85 34.25 38.44 41.87 44.76 47.27 49.48 51.46 53.25 54.89 56.39 57.78 59.08 60.29 61.43 62.50 63.52 64.48

Percentage Change

(%) 0.50 0.19 0.14 0.12 0.11 0.10 0.09 0.09 0.08 0.08 0.08 0.07 0.07 0.07 0.07 0.07 0.07 0.06 0.06 0.06

Table 11: The modelled peak discharge that could be expected during a particular return period flood, showing that the additional 7 Ml/day of water discharged from the Holfontein Shaft would have a negligible impact on the peak discharge volumes

In the last row of Table 11 it can be seen that the additional flow of 7 Ml/day, added to the flow of the Holfontein Stream would result in a negligibly small percentage change when compared to the predicted maximum flow rate that is expected during a particular return period storm. The maximum % change would be 0.5 % during a 1-year return period, and this percentage change would diminish down to 0.06 % for a flood with a return period of 20 years. Thus, the additional 7 Ml/day that would be added to the Holfontein Stream would result in a negligibly small change in the peak flow (during floods) of this stream. 1.6.2.6 The effect of the additional 7 Ml/day mine water on the average

flow in the Holfontein Stream Although the additional 7 Ml/day discharged from the Holfontein Shaft would have a negligibly small effect on the expected peak discharge volumes produced by a storm with a particular return period, this statement will not be true when considering the average (base) flow in the Holfontein Stream. In Section 1.2, and in particular in Graph 2 and Table 3, it was shown that the average flow in the Holfontein Stream was comparatively small (an average of only 0.366 Million m³ per year, i.e. ~1.005 Ml/day). It therefore stands to reason that, on average, an additional 7 Ml every day would make a huge difference to the average flow in the Holfontein Stream. The values shown in Table 3 were used to produce Table 12 below.






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Month

Average Run-

off (Mil.

m³/month)

Average Daily

Flow (m³/day)

Average Daily

Flow (Ml/day)

Average Daily Flow

Incl. discharge from

shaft (Ml/day)

Percentage

Change (%)

Oct 0.026 854.28 0.85 7.85 819.4

Nov 0.028 938.31 0.94 7.94 746.0

Dec 0.034 1 095.98 1.10 8.10 638.7

Jan 0.042 1 365.33 1.37 8.37 512.7

Feb 0.041 1 466.66 1.47 8.47 477.3

Mar 0.048 1 546.99 1.55 8.55 452.5

Apr 0.036 1 216.25 1.22 8.22 575.5

May 0.030 982.74 0.98 7.98 712.3

Jun 0.027 888.31 0.89 7.89 788.0

Jul 0.021 678.57 0.68 7.68 1031.6

Aug 0.016 527.24 0.53 7.53 1327.7

Sep 0.015 500.72 0.50 7.50 1398.0

Oct 0.026 854.28 0.85 7.85 819.4

Table 12: Assuming mine water will be discharged into the Holfontein Stream, the expected maximum discharge from the Holfontein Shaft (7 Ml/day) was added to the calculated daily natural flow in the Holfontein Stream and was converted to a percentage change. As can be seen from the last column, the average flow in this stream increased by about 450% during March (rainy season) to almost 1 400% during September (dry season)

From Table 12 it is clear that the discharge of 7 Ml/day from the Holfontein Shaft will have a significant impact on the average natural (base flow) flow in the Holfontein Stream. Hydrologically speaking, the statistical peak flow that may occur once every year is 8.14 m³/s (Table 11 and Graph 7). This flow of 8.14 m³/s equates to 703 Ml/day (note that this would be a natural “1 year flood” peak, which is not related to the discharge of mine water). This value is several orders of magnitude greater than the average flow in the stream, even when the discharge from the mine (second last column in Table 12 - ranging from 7.53 to 8.55 Ml/day) is added to the base flow of the stream. Although the flow, produced during the peak discharge of a storm with a return period of one year is only sustained for a few minutes, and not over a prolonged period, it does indicate that the streambed itself is capable of dealing with these types of flow rates without causing notable damage to the river channel for a short period. It must also be noted that this report evaluates the hydrology of the stream only and does not take the ecological effects on the aquatic faunal and floral life in the stream into account. Thus, from a hydrological perspective, this increased flow, over a relatively short period (and progressively increasing from 0 Ml/day to a maximum of 7 Ml/day over a 10-year period), should not have a noticeable detrimental effect on the hydrology of the stream. AED, however, acknowledges that it may have a negative ecological effect on the aquatic biota associated with the stream in its present state. The sustained discharge could also lead to an increased rate of erosion. However, the low slope of the stream between the Holfontein mine and its confluence with the Blesbokspruit should counter the effects of erosion.






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1.7 Holfontein Shaft Water Balance

1.7.1 Inflow into Holfontein Mine

There are essentially three water sources that would be entering the Holfontein Operations. The first, and probably the largest volume would be the water ingress of an estimated 7 Ml/day entering the underground mine workings. This water will be pumped to surface, treated and discharged into the Holfontein Stream after treatment. Obviously, this will be subject to the issuing of a Water Use Licence (WUL) by the Department of Water and Sanitation (DWS). The second stream of water would be drinking water, which would be trucked to the shaft from the ME operations. The last water source entering the Holfontein Mine would be rainwater. Groundwater ingress: The estimated peak volume of 7 Ml/day mine water entering the underground mine workings will be pumped to surface where it will be treated in a water treatment plant prior to discharge. The required water quality is yet to be determined by DWS. The type of treatment plant will be selected depending on the criteria specified by the WUL. After some treatment to remove solids and to prevent corrosion to the mine service water circuit, some of this water will be piped back into the underground mine workings to be used as mine service water (e.g. for the operation and cooling of the drills used underground, for washing purposes and for several other mining purposes). The spent water will then gravitate to the deepest part of the mine, together with the groundwater seeping into the mine workings, where it will be collected in an underground mine water dam, after passing through a settling dam, and then pumped to surface, to complete the surface-underground water reticulation circuit. Not much, if any of this mine service water will actually be lost, as it is used in a closed circuit environment. The only losses likely to occur are evaporative losses, and this water would be expelled as water vapour from the Holfontein vent shaft and evaporation off the PCD surface. Currently, the ventilation engineers have not yet calculated the air throughput volumes, and subsequently the volume of water vapour that would be expelled at the vent shaft and thus an estimation of the volume of water in the form of vapour is not possible. Potable water: Potable water will be trucked to the Holfontein Shaft and pumped into the potable water tank (item 5 in Figure 4). From this tank the water will be piped to the potable water use points, including points in the underground mine workings. As the toilets will be of the chemical containerised type, as generally used underground in mines, the amount of water that would be required for these types of toilets would be limited to the small volumes of water that is






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needed to mix the chemicals in the toilets. It is more likely that the abundance of mine water would be used for this purpose rather than using potable water that has to be trucked in from the ME Operations site. There will be no change houses at Holfontein and thus, the potable water use will be limited. In the project description, it is reported that there would be two 9-hour shifts with 400 workers per shift, thus 800 people per 24 hours. It can be assumed that each person would not consume more than 5 l during a shift, which would cover actual drinking water and to mix with a dry powder, mid-shift feed energy source. Thus, the expected potable water usage will probably not exceed 4 000 l/day. The comparatively small volume of sewage water brought from underground in drums will be treated in the modular sewage treatment plant (Item 6 in Figure 4). The effluent will be discharged together with the treated underground mine water. Rainfall: Rainwater falling on the mining area will be routed into two separate storm water systems. The first, and largest of these systems, will direct clean rainfall from uncontaminated areas directly to one or more storm water drains, which will discharge into the Holfontein Stream, either directly or via the Holfontein Tributary (refer to Figure 7 for the direction of surface water flow from the Main and Vent Shafts at Holfontein). The second and smaller storm water system will collect contaminated water from potentially contaminated surfaces (refer to the potentially contaminated surfaces and run-off volumes listed in Table 8). This water will be drained via a silt trap/settling pond to the PCD, from where it will returned to the mine service water circuit.

1.7.2 Water leaving the Holfontein Mine

Water will leave the Holfontein Mine as discharge to a surface stream, as water leaving the site in the form of interstitial water (i.e. water "stuck" to the ore or waste rock, transported to NKGM) and as evaporation, mainly through the Holfontein vent shaft, but also small volumes of evaporation from exposed water surfaces, such as the PCD. Discharge into the Holfontein Stream: This section assumes that mine water would be discharged into the Holfontein Stream. This may not necessarily be the case. In the project description document, it is estimated that the ingress into the mine will reach a volume of ~7 Ml/day. Some of this water will be used in the internal mine service water circuit for drilling and washing, but the spent water will find its way back to the mine water circuit and will again be pumped to surface, where it will be treated to a quality that is in line with the WUL (which has yet to be formulated) issued by DWS, and discharged into the Holfontein






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Stream. Thus, an estimated volume of 7 Ml/day (minus underground evaporation) will (likely) be discharged into the Holfontein Stream. The outflow will essentially be the same as the inflow, minus the evaporation via the vent shaft, which could account for a considerable volume of water and which depends on the Kilowatts of fan capacity that would be used at the vent shaft. At present, these values are not known. Upon reaching the surface, the groundwater will be subjected to treatment in the underground water treatment plant (item 20 in Figure 4), to a quality as indicated by the mine's WUL, and then discharged directly into the Holfontein Stream, or to another discharge point, as may be required by the WUL. Evaporation: As discussed above, some of the water in the mine (mine service water and/or groundwater entering the underground mine workings) will evaporate and will be discharged as water vapour by the fans at the Holfontein vent shaft. Additionally, some water will be lost through evaporation off exposed water surfaces such as off the PCD. Given the small nature of this mining operation, these volumes are almost negligibly small. Obviously, there will be other water uses that would also eventually be lost as evaporation. Here reference is made to (e.g.) people using a hosepipe to clean surfaces, the run-off of which would likely enter a storm water drain, discharging to the PCD or to the Holfontein Stream, depending on whether this surface contains contaminating substances or not, but some water remaining on the wet surface will simply evaporate. Once again, given the limited magnitude of this mining operation, these volumes will be negligibly small. Interstitial Water: Interstitial water is water that is "stuck" to rocks or sand, such as the ore and the waste rock transported to the ME Operations site. Underground gold mining occurs in a wet environment and all rock material (waste rock and ore) is mostly saturated with water. The water fraction could account for 3 to 5% of the total mass of the material transported out of a mine. In this instance, a mass of ~5% of the total mass will be used. Thus, a fair volume of water could leave the Holfontein Mine as interstitial water. It is stated that the mine will hoist at a rate of 1200 T/day, and 23 days per month. Thus, in a month the mine will produce 27 600 Tonnes of ore. Of this 27 600 T, water will account for ~1 380 T (i.e. 1 380 m³, say 2 000 m³). Water flowing off potentially contaminated surfaces, which would include the entire concrete slab around the shaft, winders and truck loading area, will be drained to the PCD. Before reaching the PCD it will pass through a silt trap to separate the solids from the liquid component. This silt will be transported together with the ore to the gold plant at NKGM. As with the ore, some water will remain as interstitial water (stuck to the silt: ~30% of the total wet mass of






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silt material) and this water will leave the water circuit of Holfontein. As stated above, this volume will actually be very small. Overall, the only really significant volume in the water balance will be the 7 Ml/day of groundwater ingress into the mine. All other water in the circuit will be comparatively minute, compared to the groundwater volumes. At this stage the water balance is still incomplete, with some of the volumes still unknown. However, using the known volumes, an underground/surface water balance diagram can be presented, as shown in Diagram 1.






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Diagram 1: The Holfontein Gold Mine provisional water balance diagram (Drawing courtesy:

Royal HaskonIngDHV, Drawing No D31430-0002-

RevC, 09/04/2015)






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1.7.3 Mine water discharge options

The original scope of work for the baseline study (that preceded this EIA study) suggested that surplus underground water would be pumped via a pipeline to ME, where it would be discharged into the Blesbokspruit. DWS, however, informed the project team that the Holfontein Project should address its own water concerns, and advised them to consider the option of discharging surplus mine water into the Holfontein Stream. As it is the most obvious option for the Holfontein Mine, this report focussed primarily on the discharge of mine water directly into the Holfontein Stream at a point close to the mine infrastructure. From a purely hydrological perspective, this option should not produce any severely negative effects on the stream, particularly as the water will only be discharged for a comparatively short period (maximum of 10 years). Furthermore, the anticipated maximum of 7 Ml/day of flow from the shaft will only be reached well into the mining phase of the project, in other words, this volume would not flow from day one of the project, but would rather increase progressively until the maximum flow is reached, several years after mining commences. It is furthermore anticipated that the actual volume of surplus underground water that would enter the mine workings is more likely to be around ~3 to 4 Ml/day, with 7 Ml/day being the "worst case scenario". Obviously, this smaller volume would also have a significantly smaller impact on the hydrology of the Holfontein Stream, when compared to the 7 Ml/day that has been used throughout this report. It was initially thought that the gradual increase in flow would allow for aquatic vegetation and aquatic invertebrates to adapt to the gradual change of the aquatic conditions in the stream. However, the aquatic impact assessment report (SEF, 2015) suggests that the higher flow in the stream could lead to negative impacts on the biological integrity of the stream. For this reason the SEF, 2015 report suggests that an alternate site (for mine water discharge) be evaluated in addition to the option of discharging water directly into the Holfontein Stream. In this report, it is suggested that water from both the mine water and sewage water treatment plants be piped to the haul road crossing and that the mine water be discharged at this crossing directly into the Blesbokspruit. From AED's perspective of the two streams (Holfontein Stream and Blesbokspruit), it is obvious that discharge directly into the Blesbokspruit would be the better environmental option. However, there are a few issues that must be considered when choosing this discharge point. These issues are as follows:

As far as water quality is concerned, the Blesbokspruit at the haul road crossing is in an excellent condition. Referring to results of the water






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sample at the haul road, shown in Table 13, Section 2.2, and judging by the determinants associated with gold mining, the Blesbokspruit in this area had the best quality water of all the sites sampled. With a sulphate concentration of only 6 mg/l, there was no indication of gold mining impacts in the Blesbokspruit upstream from, and at, the haul road crossing. Thus discharging gold mining-related water at this point in the Blesbokspruit would probably not be the best environmental option for this reach of the Blesbokspruit, unless the mine water is treated to a standard equivalent to the water quality at this sampling point. The Blesbokspruit water quality downstream from the confluence with the Holfontein Stream is affected by the effluent discharge from the Municipal WWTW. Further downstream at and downstream from the confluence with the Cowles Dam stream (an unnamed tributary of the Blesbokspruit), the Blesbokspruit is affected by historic mine water discharge from Grootvlei Gold Mine and by other industrial effluents. Immediately downstream from this confluence there are four large tailings dams at Grootvlei GM, all of which are constructed within the riparian zone of the Blesbokspruit, two of which actually extend at least to the centre of the watercourse. Thus, the Blesbokspruit is considered uncontaminated from its origin up to the confluence with the Holfontein Stream. It is further relatively uncontaminated (by gold mining) from this confluence to a point ~1.8 Km downstream, i.e. to the confluence of the Cowles Dam stream with the Blesbokspruit.

Discharge of underground water into the Blesbokspruit at a point

further downstream from the Holfontein Stream confluence (i.e. almost directly opposite the WWTW), would allow the upstream section of the Blesbokspruit to remain unaffected by mine water discharge. Discharged mine water may also impact positively on the overall water quality here; as sewage effluent and mine water discharge have complementary effects – with the chemical oxygen demand (COD) in the sewage effluent and sulphates in the mine water being diluted overall.

From a hydrological perspective, and particularly from an increased

flooding perspective, the downstream reach of the Blesbokspruit between the study area and Nigel (which includes the Marievale Bird Sanctuary and Ramsar site) is SEVERELY affected by anthropogenic impacts. There are numerous roads, railroads, pipelines and footpaths, in various states of repair/disrepair, criss-crossing the Blesbokspruit and its wetland zones at all angles. Mining and other industrial tailings dams, together with all sorts of other structures, have been constructed in the flow path of the Blesbokspruit. The reduced flow caused by these obstructions, together with the enriched (eutrophic) effluents discharged into the Blesbokspruit by numerous industries are largely the cause of the proliferation of reeds and bulrushes that have established in this reach of the Blesbokspruit. Together with its






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extremely low slope and the effects of historic sediment-rich effluent discharges into this reach of the Blesbokspruit, the proliferation of aquatic vegetation has increased the roughness coefficients by several orders of magnitude, which, in turn, have caused a permanent water level rise in the Blesbokspruit. Due to the wide floodplains, which now have become permanent wetlands, the flowing water in the Blesbokspruit would not reach a velocity where the reeds are pushed flat, which, if this had occurred, would have allowed floodwaters to pass more freely over the flattened vegetation. Only limited flattening of reeds would occur in certain areas during a flood with a return period of 100 years. For the same reason, farmland that used to lie above the flood levels of the Blesbokspruit is now inundated, either permanently or regularly. It is likely that when the Welgedacht SH were proclaimed, there were no flooding issues on the Blesbokspruit side of the smallholdings. It is AED's contention that the historic alterations to the Blesbokspruit are mostly responsible for the more-frequent flooding experienced at the Welgedacht SH. From a flooding perspective, it would therefore be better to discharge water into the Blesbokspruit some distance downstream from the Holfontein Stream confluence. Thus, the haul road discharge point may not be the best environmental option, based not only on the water quality in the reach of the Blesbokspruit up to the Municipal WWTW, but the additional volume of up to 7 Ml/day could potentially increase the flooding circumstances at the lower-lying smallholdings at Welgedacht SH, even though it was shown in Section 1.5.2.5 that the increased effect of flood events (flooding increasing by less than 1 cm, the resolution of the software used for flood modelling) would probably go unnoticed.

After considering the above issues, the discharge at the haul road should be discounted as a potential alternative discharge point, as it triggers both water quality, and hydrological (flooding) issues. This leaves two remaining alternative points of discharge:

o The first alternative is to pipe the Holfontein Shaft effluent to the

Phlox Road culvert (Refer to Figure 14). The culvert is constructed on an elevated concrete foundation and the water level downstream from this concrete foundation is about 1 m lower than the water level upstream in the Holfontein Stream. Essentially, under normal flow conditions, the water level downstream from the culvert is the same level as the water level in the adjacent Blesbokspruit. It can actually be expressed as that, under normal flow conditions, the Blesbokspruit pushes up into the Holfontein Stream up to the Phlox Road culvert. Thus discharging mine water downstream from the culvert would be the same as discharging the mine water directly into the Blesbokspruit in the same vicinity. In Section 7.1.6, where the impact of the haul road on the flow in the Blesbokspruit is






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discussed, it will be shown that the discharge in the Blesbokspruit off a 10-year flood would be 164.5 m³/s, increasing to 365.8 m³/s for a flood with a return period of 100-years. To put the 7 Ml/day into perspective, 7 Ml/day equates to 0.081 m³/s (or a mere 81 l/s). This 81 l/s would not be noticed during a 10 year flood, when the discharge in the Blesbokspruit at the same place would be 164 500 l/s. (81 l/s is ~0.05% of 164 500 l/s). However, theoretically there would be an increase in the discharge in the Blesbokspruit, and to avoid any accusations of the mine increasing flooding by any margin at the Welgedacht SH, it is advised that this option also be discounted.

o This leaves the only option that should comply with all the

triggering mechanisms, discussed above, i.e. discharging the mine water into the Blesbokspruit downstream from the Holfontein Stream. The most suitable point of discharge would be opposite the Municipal WWTW, i.e. in the triangle formed in the Blesbokspruit by two railway line embankments. This is the same area in which the WWTW discharges its treated effluent. It was stated in the above paragraphs that mine water and sewage effluent could, in fact, be complimentary to each other, purely from a dilution point of view. The mine water would dilute the COD and other nutrients in the sewage effluent, while the sewage effluent would dilute the mining-related determinants, notably the sulphate, in the mine water. Discharging the mine water in the same triangle would ensure proper mixing of the two effluents, before leaving the area. The only down-side relative to this discharge point would be the comparatively long pipeline required to reach this point and also the permissions that would be required form the landowners over whose properties the pipeline would have to pass. It is AED's contention that this option is the best option that should suit all the role players and that would trigger the least environmental issues.

Thus, in summary, there are four options for mine water discharge points from the Holfontein Shaft. These are 1) Directly into the Holfontein Stream at the shaft, 2) the Blesbokspruit at the Haul Road, 3) the Holfontein Stream downstream from the Phlox Road culvert and 4) the Blesbokspruit opposite the WWTW. The pros and cons of the four discharge points are listed in Table 13.






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Discharge

PointAdvantages Disadvantages

Closest to the mine, easily maintained Increased potential for stream channel erosion

No pipeline required. No maintenance on pipeline

required

Potential negative impact on aquatic life, as stream will change

character from a non-perennial to a perennial stream

Potential to dilute effluent in Holfontein Stream from

upstream landfill site

Increased base flow in Holfontein Stream. Culverts at Phlox

and Carnation Roads will have to be upgraded to

accommodate the increased flow

There is no pipeline that needs to be constructed before

dewatering from the shaft can commence

Potential increased aquatic vegetation due to the nature of the

stream changing, resulting in a proliferation of aquatic plants,

notable bulrushes and reeds, interfering with the culverts at

Welgedacht SH, as well as at the provincial road (Poppy Road

extension). This will result in increased maintenance to

remove vegetation that could interfere with the functioning of

culverts

Although the increase in flood elevations would be very small,

this option would nevertheless expose the mine to potential

litigation due to natural flooding at the Welgedacht SH.

Pipeline would follow an existing servitude for the haul

roadLong pipeline required. Additional maintenance on pipeline

Maintenance of pipeline would be simple as it follows the

haul road. No access issues

Mine water would decrease the good water quality in the reach

of the Blesbokspruit from its origin up to the Municipal WWTW

discharge point

Blesbokspruit can accommodate the additional water for

both base flow and flood peaks without erosion

Although reality insignificant, the flood elevations at the

Welgedacht SH would still be an area of concern and mine

could still be accused of increasing the flooding potential at the

low-lying smallholdings closer to the Blesbokspruit

Dewatering from the shaft can only commence once the

pipeline to the discharge point has been constructed

Discharge would not occur into Holfontein Stream, but

into canal at a water level corresponding to the elevation

of the Blesbokspruit in the same area, i.e. at a lower

elevation than the water in the Holfontein Stream

upstream from the Phlox Rd culvert, thus increased risk

of flooding would be eliminated in the Holfontein Stream

Although an increase in flood elevations in the Holfontein

Stream would be eliminated, increased flood elevations in the

Blesbokspruit would still be an issue for the low-lying

smallholdings at Welgedacht SH, and even though the

increased flood elevations would be negligibly small, the mine

could still be blamed for losses during flooding episodes

Long pipeline required, additional maintenance on pipeline



The reach of the Blesbokspruit into which the mine water

would be discharged is part of the upper Blesbokspruit which

has a high water quality. Mine water would decrease the water

quality in the remaining ~1.8 Km of the uncontaminated reach

of the Blesbokspruit

Blesbokspruit can accommodate the additional water for

both base flow and flood peaks without erosion or

increased elevation in water level

Long pipeline required, additional maintenance on pipeline

Mine water would be discharged downstream from the

uncontaminated reach of the Blesbokspruit, i.e. into an

already impacted reach of the Blesbokspruit

Pipeline potentially passing over private property

Mine water could dilute certain determinants in the

sewage effluent (COD, nutrients, etc.), while the sewage

effluent would dilute the mining determinants (such as

sulphates and calcium) in the mine water



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Table 13: A summary of the advantages and disadvantages pertaining to the different points of mine water discharge






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2. Surface Water Quality

2.1 Surface water monitoring

The Holfontein Shaft was closed many decades ago, long before 1956, and as such, no records are available to indicate how much water was discharged from the shaft and what the water quality was when it was discharged. In fact, in the introduction of this document it is stated that this shaft was already operational in 1937. Long after the shaft was closed, the Holfontein Hazardous Waste Landfill Site was established. The unnamed stream passing the Holfontein Shaft, referred to as the Holfontein Stream for the purposes of this document, rises in the area now occupied by the landfill site. Although the landfill site would have a good surface- and groundwater-monitoring programme in place, there is still a likelihood that contamination from the landfill site could reach the reaches of the Holfontein Stream downstream from the landfill site and thus, it is necessary to record the water quality in the Holfontein Stream independently from the management of the landfill site. It is AED's contention that, in spite of several years of gold mining at this shaft, the time that has lapsed since the shaft was closed and the fact that the waste-rock dump and all other deposits had been removed from the site suggests that the water quality in the Holfontein Stream is likely to be in a condition similar to what it was prior to commencement of mining at the shaft. This excludes potential contamination from the hazardous waste landfill site. The "signature" of contamination from a hazardous landfill site would be different from that of a gold mine in Witwatersrand rocks (or of Black Reef rocks also mined in these areas), and thus, it would be possible to differentiate between the two types of contamination. To ensure that a proper baseline water quality record of the water in the Holfontein Stream is registered before mining activities re-commence at the shaft, several water samples were collected during a site visit on 03/03/2015. These samples were analysed by a SANAS-accredited analytical laboratory. The results of these samples are recorded in Table 14. Unfortunately, the collection of these samples coincided with a particularly "dry" rainy season experienced in these parts of South Africa. Thus, it is likely that the flow in the stream was lower than what it should have been on average during the latter parts of an average rainy season, pre-empting that monitoring (before during and after mining) is essential. It was noted that, although there was surface flow in all the upper reaches of the Holfontein Stream, there was no flow at the last sampling point where the stream reaches the elevation of the Blesbokspruit, i.e. immediately upstream from its confluence with the Blesbokspruit. It must therefore be taken into account that during a "normal" rainy season, the flow in the stream could be greater. More importantly, the dams in the upper reaches of the Holfontein Stream






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immediately downstream from the landfill site would have been overflowing, which was not the case when these samples were collected.

2.1.1 Description of the sampling points

To assess the water quality in the Holfontein Stream, three water samples were collected from this stream, while a fourth sample was collected from the Blesbokspruit at the point where the proposed haul road between the Holfontein Shaft and the ME Operations passes over this stream. These samples were submitted to DD Science, a SANAS-accredited analytical laboratory, for analyses. A summary of the results is presented in Table 14 and the laboratory analyses report is attached in Appendix 2. The sampling sites are shown in Figure 3 on Page 8 of this document. 2.1.1.1 Sample Holfontein 1 This sample was collected from a dam, ironically named the "Lushof Dam", located immediately downstream from the Holfontein hazardous waste landfill site, and upstream from the Holfontein Shaft. When the Afrikaans name, "Lushof" is translated directly into English, it means something like "garden" or "yard of delight". It is obvious this name was given before the landfill site was established, as this area is now all but a place "of delight".

Photo 2: The Lushof Dam in the Holfontein Stream, from which Sample, Holfontein 1 was collected, locates immediately downstream from the Holfontein Hazardous Waste Landfill Site






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Photo 3: Part of the Lushof Dam in the Holfontein Stream to the right of the photo, from which Sample, Holfontein 1 was collected, with a small part of the Holfontein Landfill Site on the horizon. This photo was taken viewing upstream towards the Holfontein Hazardous Landfill Site

It can be expected that any leachate or surface run-off emanating from the landfill site would be present in the water of this dam, hence the sample. Due to the below-average rainfall at the time the sample was collected, the dam was not overflowing when the sample was taken. 2.1.1.2 Sample Holfontein 2 This sample, Holfontein 2, was collected from the Blesbokspruit where the proposed haul road passes through the Blesbokspruit wetland and over the Blesbokspruit. This is an existing but "informal" road. The bridge is just as "informal". It comprises of a 1-m pipe laid in the stream channel and then filled up with soil over the pipe to elevate the road above the water level in the stream. The approaches to the "bridge" over the swampy surface of the wetland are the same construction, i.e. the wetland was filled up with soil to form a hard surface on which vehicles can drive. This sample is representative of the Blesbokspruit upstream from the historic gold mining activities (mainly the Grootvlei Mine). This part of the Blesbokspruit should theoretically be closer to its pristine condition, when compared to the reaches further downstream, although there is an existing sewage plant at Etwatwa, which could possibly have an impact on the water quality upstream from this sampling point. Surface run-off from Etwatwa, Daveyton and surrounding






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high-density urban areas may also have a negative impact on the water quality in this reach of the Blesbokspruit.

Photo 4: Sampling site, Holfontein 2, where a very "informal" road passes through the Blesbokspruit wetland and over the stream channel itself. The equally informal "bridge" over the Blesbokspruit channel consists of a 1-m pipe placed in the stream channel and filled up with soil to the same elevation as the approaches to the bridge through the wetland

2.1.1.3 Sample Holfontein 3 This sample was collected from the Holfontein Stream where it flows under the Pansy Avenue Bridge. Thus this sample represents the water quality in the Holfontein Stream downstream from the Holfontein Shaft. Although the stream was flowing when the sample was collected, the actual stream was totally obscured by the dense bed of bulrushes (Typha capensis) and common reeds (Phragmites australis).






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Photo 5: The sampling site, Holfontein 3, where the Holfontein Stream flows under the bridge where Pansy Ave passes over the stream. Although the stream was flowing when the sample was collected, the actual stream was totally obscured by the dense bed of bulrushes (Typha capensis) and common reeds (Phragmites australis), as is evident from this photograph

2.1.1.4 Sample Holfontein 4 This sample was collected at the culvert where Phlox Road, in the Welgedacht SH, passes over the Holfontein Stream. This is the furthest downstream point where a sample representing the Holfontein Stream water quality can be collected. Downstream from this bridge the water table in the Holfontein Stream is at the same elevation as the water in the Blesbokspruit, thus, a sample collected on the downstream side of the culvert would not be representative of the water quality of the Holfontein Stream, but rather of a mixture of the Holfontein Stream and the Blesbokspruit. There is a slight elevation difference between the in- and outlets of the culvert where the sample was collected, due to a concrete slab on which the culvert was constructed. The sample was collected from the upstream side of the culvert. The stream was not flowing over the concrete slab under the Phlox Rd culvert, suggesting that the water collected for the sample could be representative of the surface run-off from a small thunderstorm that fell over the Welgedacht SH during the previous night, and not necessarily that of the Holfontein Stream as such.






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Photo 6: The upstream view at sampling site, Holfontein 4, showing that the stream was not flowing over the concrete slab in the foreground of the picture

Photo 7: The Downstream view from the sampling site, Holfontein 4. Essentially the rest of the stream flows in a canal up to its confluence with the Blesbokspruit. The water surface elevation in this stream is the same as the elevation of the water in the Blesbokspruit, implying that a sample from the downstream side of the culvert would not be representative of the Holfontein Stream's water






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2.2 Discussion of the water quality

Table 14 is a summary of the water quality at, and associated with, the Holfontein Shaft during the summer 2014/2015 rainy season. The samples were collected on 03/03/2015. The sample results were compared with the South African National Standard, SANS 241:2011 – Edition 1.0. SANS 241 is the official South African drinking water standard. The 2006 version of this standard provided 2 levels of quality, Recommended (Class I) and Maximum Allowable for a limited period (Class II). The latest edition, SANS 241:2011, has simplified the standard to a certain extent by removing some of the unnecessary determinants from the standard (determinants such as calcium, magnesium and potassium that do not really pose a health hazard to humans). At the same time the standard has been brought in line with international standards (World Health Organisation) and the concentrations of some determinants were increased or decreased. The most important change, however, was the abandonment of the different classes (or concentration ranges) in the standard. These classes (or varying degrees of “grey” between “good” and “bad”) caused unnecessary confusion in the past. In only a few cases does SANS 241:2011 quote more than one value for a particular determinant, but this differentiation is only used to distinguish between aesthetic, operational (water treatment plant parameters) and health parameters. For ease of identification, we have colour coded the entries in Table 14. If a determinant complies with SANS 241:2011, it is colour coded green, if it exceeds only the aesthetic or other non-health concentration, but still complies with the health concentration, it is coloured yellow, while determinants exceeding the health concentration are coloured orange. If there is no standard for a particular determinant, it is left white. If a determinant is listed in the 2006 version of the standard but not in the 2011 version, and the 2006 Class I range is exceeded, we also colour-coded it yellow. The sampling points reported on in Table 14 are shown in Figure 3.

A note on the use of SANS 241 (2011): It must be kept in mind that the SANS 241 Standard is a drinking water standard intended to gauge the suitability of a water supply at the end-point drinking water user. It was never intended for assessing industrial effluent or mining-related water. However, as this is the best available standard (not a guideline, but a standard, enforceable by law) it is commonplace to also use this standard as a guide for assessing water found in the environment in order to determine the performance of a water user. It must, however, be granted that AED (and most other environmental practitioners) use this standard as a guideline and not as an enforceable standard, in this case, to assess the quality of the water in the Holfontein Stream and Blesbokspruit at, or in close proximity to the Holfontein Shaft.






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Table 14: The chemical analyses results of the surface water samples, collected from the Holfontein Stream and Blesbokspruit in areas associated with the Holfontein Shaft

1.2.1 General discussion of the surface water quality at the study area

In general, the water quality in the Holfontein Stream and the Blesbokspruit was rather good, with only the ammonia exceeding the SANS 241:2011 standard marginally in all four of the samples. The ≤1.5 mg/l standard limit is set on an aesthetic (taste and smell) basis and is not as a health risk. It must, however, be noted that the highest ammonia concentration was recorded at the sample closest to the landfill site.






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The manganese in sample Holfontein 3 (of 1 543.6 µg/l) exceeded the standard limit by a significant margin. However, the Holfontein 3 sample was collected among the bulrushes and decomposing vegetation near the bottom of the stream (see Photo 4). It is likely to encounter anaerobic and reducing conditions in this zone of a stream due to the presence of decomposing vegetation and thus, there is no reason for alarm relating to the manganese concentration at this sampling point. The pH of this sample was also the lowest of the four samples (pH 7.4), which, together with anaerobic and reducing conditions in the zone from which the sample was collected, could also have played a role in dissolving this metal. Unlike iron, once in solution, manganese is more readily stabilised by complexation and will not readily precipitate out of solution, as iron would. Thus, the fact that the iron concentration is low compared to the manganese concentration suggests that this is what had occurred at this sampling point. The aluminium concentration of 369 µg/l at sampling Point, Holfontein 4, exceeded the SANS 241:2011 standard limit of 300 µg/l. This is a very small margin and, given that aluminium is the most common metal in the Earth's crust, having an abundance of 81 g/Kg, this concentration should not be interpreted as indicative of any areas of concern. As described in Section 2.1.1.3, the water in the stream at this sampling point was more likely local surface water run-off from one of the smallholdings in the Welgedacht Smallholdings, rather than actual flow in the stream from its upper reaches. Although not triggering the SANS 241:2011 standard, the very high pH at sample, Holfontein 1 (pH 9.1) is, in our opinion, more of an area of concern than the other determinants that exceeded the standard limit. This is by no means natural in these parts of South Africa. The pH of a stream so close to its origin, flowing off sandstone of the Karoo Supergroup should be in the high 6's to mid 7's and not near pH 9. It can only be assumed that the Holfontein landfill site is responsible for this high pH. The conductivity/TDS at this sampling point was also the highest of the four samples, indicating an impact from the landfill site. So too was the sulphate, chloride, calcium, sodium and potassium, further supporting the impact from the landfill site. However, none of these determinants actually exceeded the SANS 241:2011 standard limit. We actually expected the water in the Lushof Dam to be much more polluted than what was recorded, indicating that the Holfontein Hazardous Landfill Site must have a very good environmental protection policy in place. The Total Dissolved Solids (TDS) results in Table 8 were also compared with the DWA National Database for quaternary catchment C21D. In terms of the DWA National Database, as documented during the WR2005 (WR2005 - Middleton & Bailie, 2005) project, the TDS in the Holfontein Stream is expected to be very low (refer Figure 16). However, on closer inspection, the light blue shading of the Suikerbosrant River Catchment is reflected as "-1" in the WR2005 dataset, which placed it in the lowest possible TDS range (light






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blue). This, is, in fact, an error and does, in fact, not indicate low TDS, but rather "No Data". It is AED's contention that there should not be much of a difference between the Suikerbosrant River Catchment and the two catchments adjacent to it, the Rietspruit catchment to the west and the Waterval River catchment to the southeast. In other words, the TDS in the Suikerbosrant River should be in the dark orange shaded range of 450-650 mg/l and not at all in the light green shading.

Figure 16: The Total Dissolved Solids (TDS) in the Vaal River catchment (upstream from the Vaal Barrage Dam and including the Blesbokspruit and Holfontein Stream catchments). Note the very high quality water (low TDS) in the Suikerbosrant River catchment (including the Blesbokspruit and Holfontein Stream catchments), indicated by light blue shading, compared to the darker orange shades of the adjacent catchments. This very high quality is in fact, an error in this record set. In this instance, the light blue shading does not indicate low TDS, but rather "No Data"

The last column in Table 14 shows the average water quality in the actual Holfontein Shaft. The average results were made up of three samples, which






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were collected from three different depths by Shango Solutions on 20 November 2014 (Handley, 2014). At the time of sampling, the water level in the shaft was 112 m below surface. The three samples were collected at 115 m, 215 m and 300 m below surface in the shaft. The analyses of these three samples were close to being identical and thus an average was recorded by Handley. In this document, the shaft bottom is in excess of 315m below surface. The average results were compared with the SANS 2341:2011 standard limit. None of the determinants exceeded the standard limits. Thus the water in the shaft is of a particularly good quality. However, from the author's experience with mine water decanting from the Western Mine Void Basin during 2002, this water quality at the Holfontein Shaft is no indication of the ultimate quality that could be expected once water is drawn from the haulages and stopes. In the case of the Western Basin, the initial quality of water decanting from the mine was good. However, this was the dolomitic water overlying the mine water being pushed out first before the deeper mine void water. After a few months the water quality began deteriorating to the levels where the sulphate concentration in the decanting water was in the range of 4 000 to 6 000 mg/l, typical of acid mine drainage (AMD). The calcium and magnesium concentrations in the mineshaft water suggest that this water is dolomitic water with a small volume of mine water mixed with it. Although it does not report on the temperatures of the samples, the Shango report suggests that there was no stratification in the shaft. We do not know the actual Holfontein GM void space (i.e. the volumes of all the flooded haulages and stopes combined). Thus, it is dangerous to speculate on what the water quality may do once shaft dewatering begins. It must, however, be accepted that the water quality pumped from the deeper parts of the mine will certainly not be the same quality of the water in the shaft itself.

2.3 An interpretation of the samples at the Holfontein study area, using Hydrochemical Imaging

There are several methods of presenting an image of the hydrochemistry, in order to interpret water chemistry in a visual arrangement. The most popular of these imaging methods are the Piper, Stiff, Durov and Expanded Durov Diagrams. From our perspective, all these diagrams ultimately demonstrate the same thing. To avoid confusing imaging, we have thus standardised on using the Piper Diagram, as, in our opinion, it is the simplest to understand and to interpret. The Piper Diagram shown in Figure 17 illustrates the character of the water samples, collected from the streams at the Holfontein study area. The Piper






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Diagram, introduced by Arthur Piper in 1944, is one of the most commonly used techniques to interpret water chemistry data. Although originally intended as a tool for groundwater only, the Piper Diagram is just as useful in interpreting surface water quality, especially if mining activities have impacted upon the water quality in these streams. This method comprises of the plotting of cations and anions on adjacent tri-linear fields, with these points then being extrapolated to a central diamond field. Here the chemical character of water, in relation to its environment, can be observed and changes in the quality interpreted. The cation and anion plotting points are derived by computing the percentage equivalents per million for the main diagnostic cations of Ca2+, Mg2+ and Na+/K+, and anions Cl-, SO4

2- and CO32-/HCO3

-. Different waters from different environments always plot in diagnostic areas or “hydrochemical facies”. The upper half of the diamond normally contains water of static and disordinate environments, while the middle area normally indicates an area of dissolution and mixing. The lower triangle of this diamond shape indicates an area of dynamic and co-ordinated environments. Sodium chloride brines normally plot on the right hand corner of the diamond shape while recently recharged water plots on the left-hand corner of the diamond plot. The top corner normally indicates water contaminated with gypsum (SO4

2- mine impact). In general the top half of the diamond contains static waters and other unusual waters high in Mg/Ca Cl2 and Ca/Mg SO4. The lower half contains those waters normally found in a dynamic groundwater basin or surface stream environment. Mixtures of any two waters in any proportion plot along a straight line joining their respective points in each of these diagrams. Water therefore being invaded by e.g. an industrial effluent will plot a vector towards the analysis of the invading fluid. Water plotting in the upper half of both the cation and anion triangles would be referred to as magnesium sulphate-type water. Water plotting in the lower left hand side of the cation triangle and the lower right hand side of the anion triangle would be calcium chloride-type water. If both cation and anion compositions plot in the middle of the two triangles, then the waters would be referred to as mixed cation-mixed anion-types. If water plots near the middle of one of the edges of the triangles, then one might refer to, e.g., magnesium-calcium sulphate water. If waters are the result of mixing of two different end member waters, then the compositions of these waters should plot along a straight line in each of the fields of the diagram. On the other hand, if the compositions do not plot along a straight line on the Piper Diagram, then the waters cannot be related by simple mixing between two end members. If the waters do plot along a






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straight line, this is not necessarily definitive proof that mixing did occur, but it is strongly suggestive and other tests can be designed to prove mixing. Unpolluted rainwater will plot in the left-hand corner of the central diamond field of the Piper Diagram. As this water flows over or through the substrate, it accumulates minerals from this substrate over or through which it flows and the point where it plots will move across the central diamond field of the Piper Diagram and, depending on which mineral/s act/s on it, will either move up or down in the diagram. On the other hand, when water flows through a wetland where ion exchange and adsorption occurs, in addition to the vegetation removing some of the minerals from the water, samples could move across the Piper Diagram in an opposite direction to what is described in the above paragraph. For ease of identification, we have annotated some of the general areas in the Piper Diagram in Figures 17.

Figure 17: The Piper Diagram of the samples from the Holfontein study area

When studying the cation and anion triangles, it is evident that Holfontein 4 sample (at Welgedacht Smallholdings) is a calcium-bicarbonate type water (i.e. similar to rainwater), the Holfontein 2 (Blesbokspruit) and Holfontein 3






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samples are classified as a calcium or sodium-bicarbonate type waters, while the Holfontein 1 sample (Lushof Dam near the landfill site), is a sodium chloride type water. When the points where the samples plot in the cation and anion triangles are extrapolated onto the central diamond field of the Piper Diagram, it is observed that the samples plot in two distinct groups. The first group, included in the green circle, plot roughly where "ideal" types of waters should plot, i.e. in the area just adjacent to the area annotated as "recently recharged water". This is where rainwater would plot if it has spent a comparatively short period in a surface stream. It has acquired some mineralisation from the substrate over which it has flowed, pushing it slightly across the Piper Diagram towards the area annotated as an "area of dissolution and mixing". We have no concern with these samples. The fourth sample, that of Holfontein 4 (Lushof Dam downstream from the landfill site) plots in a group of its own, i.e. edging towards the sodium chloride area of the Piper Diagram. This definitely indicates some sodium contamination off the landfill site. Overall, there is no indication of gold mining related contamination in the Holfontein Stream or in the Blesbokspruit where the planned haul road crosses over the stream. This fact must be noted, as these samples will be representative of the conditions before new mining activities begin at the Holfontein Shaft. It appears that no legacy of whatever pollution may have occurred during the heydays of mining at this shaft is present today in any of the water samples collected.

3. The Water Quality in the Holfontein Shaft Although this water presently represents groundwater, this water will become surface water once pumped to surface. It therefore warrants discussion in this surface water report. Shango Solutions collected water samples from and carried out depth measurements in the flooded shaft during 2014. The Shango Solutions report (Handley, 2014) indicated that the water level in the shaft had stabilised at an elevation of 112 m below surface. Using the LiDAR-surveyed contour lines acquired from the Ekurhuleni Metropolitan Municipality, it was established that the slab over the shaft is at an elevation of ~1596 m above mean sea level (mamsl). Thus, the water level in the shaft is at 1481 mamsl. The water level in the Blesbokspruit at the same latitude (i.e. where the N12 freeway crosses the Blesbokspruit) is at ~1577 mamsl. This means that the water level in the shaft is well below (~96 m below) the surface water level in the Blesbokspruit and thus also well below the assumed






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groundwater table in the same region. If water flow were to occur, it would be from surface (or from the perched water table) to the Holfontein Mine void environment and not vice versa. This fact is to some extent encouraging and could indicate that infiltration from the overlying dolomitic aquifer into the Holfontein Mine void could occur at a comparatively slow rate, which could indicate that there may be less inflow into the existing underground mine workings than anticipated. The Shango Solutions report also indicated that the water in the shaft had a high quality with, e.g. sulphate in the range of 49 to 61 mg/l (average of 54 mg/l). This low sulphate concentration supports the assumptions made in the above paragraph, i.e. that the water flow occurs from groundwater into the shaft and not vice versa. This would also explain the comparatively good water quality in the shaft. It further suggests that, after mine closure and stabilisation of the water table, it is likely that water would not decant on surface locally. However, and given extensive experience in gold mining on the Witwatersrand, it is unlikely that this current status quo would be maintained once dewatering commences. It is more likely that the water quality would deteriorate, with particularly sulphate increasing in concentration. The predicted end-point sulphate concentration will depend on two potential scenarios, once mining re-commences. If the speculation in the above paragraph were correct, i.e. if a comparatively small fraction of the water ingress into the mine would be linked to the dolomitic aquifer overlying the mine workings, the volume of water that would have to be pumped from the underground mine workings would be lower than anticipated, but the water quality would be worse (likely to have a sulphate concentration in the 3 000 to 4 500 mg/l range). On the other hand, if larger volumes of dolomitic water ingress into the mine void occur, the opposite could be true, i.e. larger volume of water with a comparatively lower sulphate concentration (in the range, 1 500 to 3 000 mg/l).

4. Drainage Density of the Holfontein Stream

Drainage density is the total length of all the streams in a drainage basin divided by the total surface area of the drainage basin. It is a measure of how well or how poorly stream channels drain a catchment. It is equal to the reciprocal of the constant of channel maintenance and equal to the reciprocal of two times the length of overland flow.

Drainage density depends on both climatic and physical characteristics of a drainage basin. Soil permeability (i.e. infiltration ease/difficulty) and underlying rock type affect the run-off in a catchment; impermeable ground or exposed bedrock will lead to an increase in surface water run-off and therefore to more frequent streams. Rugged regions or those with high relief will also have a






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higher drainage density than other drainage basins, if the other characteristics of the basin are the same.

Drainage density can affect the shape of a river's hydrograph during a rainstorm. Rivers that have a high drainage density will often have a more “flashy” hydrograph with steep climbing and falling limbs. High drainage densities can obviously also indicate a greater flood risk.

The shape of a catchment will also play an important role in the drainage density. A more rounded catchment will cause all the rainwater falling on, and around the perimeter of the catchment, to arrive at the outlet of the catchment roughly all at the same time, as the distance from the edges of the circle to the outlet would all, very roughly, be the same. In such cases, the flood caused by a storm falling over this catchment will be relatively “flashy”, when compared to a narrow, elongated catchment.

On the other hand, an elongated catchment will cause much more spreading out of the floodwaters over a time period. Rainwater falling in the lower or central parts of the catchment will be long gone before the water falling in the upper reaches of the catchment arrives at the outlet of the catchment. Subsequently the flood will be less severe (less “flashy”) while the flood peak will be spread over a longer time, i.e. the river’s hydrograph will have a flat climbing and falling limb. In the case of the Holfontein Stream, the shape of the catchment (refer to Figure 6) is more rounded than elongated, which predicts more flashy floods with slightly higher flood peaks in this catchment than the average catchment of this size. High drainage densities also mean a high bifurcation ratio (higher number of division nodes of a drainage basin “tree”).

The surface area of the Holfontein Stream catchment up to its confluence with the Blesbokspruit is 25.23 Km². The total length of all the collectors in this catchment is 11.281 Km.

Thus the Drainage Density for the Holfontein Stream up to its confluence with the Blesbokspruit is 0.447 Km/Km2. (Km watercourse/Km2 of catchment or just, “/Km”). This is a comparatively low drainage density in spite of its rounded shape. This is attributable to the very low slope of the catchment.

5. Downstream Water Use The Holfontein Stream flows for a distance of about 3 Km from the N12 freeway bridge (after which impacts from the Holfontein Shaft could occur), to sampling point Holfontein 4 (after which it enters the Blesbokspruit wetland). This part of the stream can generally be divided into two sections. The first part is 2.26 Km long. Apart from the Holfontein Shaft, the area adjacent to this reach of the stream is used for dry-land maize farming. This






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form of agriculture does not require water from this stream. Only the Holfontein Shaft could be considered as being a potential water user in future, as it will likely discharge underground water into the Holfontein Stream to enable mining. The second part of the stream, downstream from the N12 is 740m (0.74 Km) long. The only potential water users in this reach of the stream are the riparian plots at the Welgedacht SH. After these smallholdings, the stream enters the Blesbokspruit wetland (at sampling point, Holfontein 4). The smallholdings with riparian rights are shown in Figure 18, an aerial photograph of the Welgedacht SH. Originally there were 18 portions in this part of Welgedacht SH. However, with the railway line, traversing Welgedacht SH diagonally from northwest to southeast, some of these portions were subdivided. After subdivision, the 18 portions became 25 portions, many of which are tiny with no commercial value. These portions are now owned by Transnet and are associated with the railway line. These portions are as follows:

Pn 1 of Pn 38, Pn 1 of Pn 39, Pn 1 of Pn 42, Pn 1 of Pn 43, Pn 1 of Pn 44, Portion 45 and Pn 1 of Pn 48

This leaves 18 smallholdings in Welgedacht SH along the Holfontein Stream. Of these 18 smallholdings, the southern 6 are not considered as users of the Holfontein Stream (but rather users of the Blesbokspruit), as the Blesbokspruit water pushes up into the Holfontein Stream canal up to Phlox Road. This leaves 12 smallholdings between Carnation Rd and Phlox Rd that could be considered as being water users of the Holfontein Stream. Of these 12 smallholdings, the remaining extent (RE) of Portion 39 is cut off from the Holfontein Stream by the railway line embankment, while the RE of Pn 42 and Pn 50 are unoccupied. Thus, there are only 9 portions that could use water from the stream. There is an old and very small farm dam in the Holfontein Stream on the RE of Pn 43, which could be considered a water use. However, there are only a few shacks on this portion and no pumping equipment at the dam, which clearly indicates that no water is used from the stream. In fact, during the site visit on 03/03/2015, AED could not find any actual water use at any of the remaining smallholdings. Thus, the only concerns relating to downstream occupants would be the increased flow in the stream should water be discharged from the Holfontein Shaft. Neither of the two culverts under the Carnation and Phlox Roads in Welgedacht SH are designed for any major storm and thus the discharge of water from the Holfontein Shaft could have a compounding effect, should this






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pumping coincide with a major storm (not necessarily a 100-year storm, but any storm with a return period greater than ~4 years). It will thus be required to increase the capacity of the culverts or to have some other contingency plan in place once pumping actually begins at Holfontein Shaft.

Figure 18: Part of the Welgedacht SH, showing the actual smallholdings, which may be considered as being water users (Aerial Photography: Ekurhuleni Metropolitan Municipality, 2009)

The 100-year flood lines modelled for this project indicate that the culvert under the railway line has adequate capacity to handle the discharge of a 100-year return period storm. However, these flood lines also indicate that the railway line embankment would cause a dam to form on the upstream side of the railway line (bridge backwater), increasing the 100-year flood lines by a






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significant margin (refer to Figure 18). This is, however, not a concern for the Holfontein Shaft; it is a Transnet issue (who constructed the railway line originally). The last issue that may have relevance to this project is the groundwater quality at all the Welgedacht SH. Although not a surface water issue, the fact that groundwater concerns could arise from surface sources necessitates its mention in this report. From the 2012 NKGM groundwater report (Botha, 2012) it is clear that the groundwater table in these areas is very shallow and that it is controlled by the water level in the Blesbokspruit. Furthermore, most of the Welgedacht SH locate on dolomite of the Malmani Subgroup, Chuniespoort Group, Transvaal Supergroup. If acidic mine water, high in sulphate, were to infiltrate into the aquifer underlying the Welgedacht SH, the rate of sinkhole formation in this area could increase. Additionally, the quality normally associated with gold mining underground water is generally poor. This scenario has been demonstrated at the Western Basin Mine Void, where the poor quality mine decant water recharges into the Zwartkrans dolomitic aquifer, contaminating the water in this aquifer. Thus, if untreated mine water from the Holfontein Shaft is allowed to infiltrate the aquifer underlying the Welgedacht SH, it could potentially contaminate the water in the aquifer and hence have a negative effect on the borehole water quality used by the residents of the Welgedacht SH. However, it is highly unlikely that DWS would allow untreated water to be discharged, thus allaying this issue to a large extent.

6. Surface Water Monitoring Programme To ensure that at least one sample is collected upstream, one immediately downstream from the mine and one at the confluence of the Holfontein Stream with the Blesbokspruit, the same three sampling points in the Holfontein Stream should be monitored on a monthly basis during the life of the mine in the Holfontein Stream. This should be done irrespective of whether mine water is discharged into the Holfontein Stream. The Blesbokspruit immediately downstream from the haul road crossing should also be monitored monthly. Water samples must also be collected/analysed prior to and during the construction phase of the mine. Additionally, the water discharged from the Holfontein Shaft must also be monitored monthly (using the EC and pH being recorded daily, using a portable instrument, which is calibrated regularly). The following points must be sampled:

Holfontein 01 (The Holfontein Stream at the Lushof Dam immediately downstream from the landfill site)






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Holfontein 02 (The Blesbokspruit immediately downstream from the haul road crossing)

Holfontein 03 (The Holfontein Stream at the Pansy Road extension bridge i.e. the first culvert downstream from the shaft)

Holfontein 04 (The Holfontein Stream at, but upstream from, the Phlox Road culvert)

Holfontein 05 (The treated mine water leaving the shaft into the Holfontein Stream)

The following determinants must be analysed for:

pH EC Total Hardness Total Alkalinity Sulphate Nitrate Chloride Ammonium Calcium Magnesium Sodium Potassium Iron Manganese and Uranium

It is furthermore also recommended that every 6 months, i.e. in July and January, coinciding with the middle of the dry and rainy seasons, an additional full ICP-MS analysis be carried out on all the samples, to determine the micro-determinants not analysed for during the monthly analyses.

7. Environmental Impact Assessment This report has shown that although the Holfontein Project will be a comparatively small operation (compared to traditional gold mines on the Witwatersrand) and will have a comparatively limited lifespan of ~8 years of production (compared to the more traditional gold mines on the Witwatersrand that had/have life spans of several decades of mining), it will still have some impacts on the surface water and hydrological environment. These issues will be discussed individually hereunder.






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7.1 Surface Hydrology of the Holfontein Stream

7.1.1 100-Year Flood Lines and mine surface infrastructure

Government Notice GN704, specifically dealing with the location of mines relative to flood lines, promulgated in terms of the National Water Act of 1998 (Act 36 of 1998), legislates that no residue deposit, dam, reservoir or any of its associated infrastructure may be placed within the 100-year flood lines or within 100 m from a river’s edge, whichever distance is the greatest. It continues that no opencast or underground mine may be located within the 50-year flood line of a stream or river (or within 100 m from the edge of a river, whichever distance is the greatest) and neither may one erect any sanitary convenience, fuel depots, reservoir or depots for any substance which may cause, or is likely to cause, pollution of a water resource within the 50-year flood line of any watercourse. In Section 1.5.2 it was shown that a storm with a 100-year return period would produce a flood with a peak discharge of 88.43 m³/s in the Holfontein Stream in the vicinity of the Holfontein Mine and at the downstream water users, the Welgedacht SH. It was also determined that the area of inundation produced by this 100-year flood (as indicated by the 100-year flood lines) would not come near the Holfontein Shaft and thus this item in GN704 is of no concern. The nearest part of the security fence around the shaft and surface infrastructure area is 368 m from the Holfontein Stream and thus also complies with the 100-m buffer of GN704. Thus, the surface infrastructure area complies in full with the 50- and 100-year flood line limitations part of GN704, i.e. no mining or ancillary items will be placed within the 100- or 50-year flood zones, or within 100m from the edge of the Holfontein Stream.

7.1.2 Mining within the 100-year flood lines

Referring to Figure 19, it is noted that historic mining has and that some of the proposed new mining will occur below the Holfontein Stream and within the 100-year food lines. As described in Section 1.5.2, in a stream with a small catchment, such as the Holfontein Stream, the vertical distance between the 50-and 100-year flood lines are centimetres apart. Thus, only the safer of the two sets of flood lines, the 100-year flood lines were modelled. These flood lines will therefore also be used in instances where the 50-year flood lines are specified in GN704. In other words, if a mining entity is outside the 100-year flood line, it is automatically also outside the 50-year flood line. Although mining will occur below the Holfontein Stream and within its 50-year flood area of inundation, it must be borne in mind that this mining will begin at 363 m below surface in the northeast around the shafts and will increase to






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645 m below surface in the southwestern extent of the proposed mining area (Figure 19). It is thus AED's contention that, due to the depth of mining, this condition of GN704 (mining within the 50-year flood lines) should not be applied in this instance, as there is sufficient solid rock material between the surface stream and the proposed mining to ensure that there will not be a direct hydraulic link between the two zones. This issue should be dealt with when the application for the WUL is carried out.

Figure 19: The existing (historic) extents of mining at Holfontein (yellow lines) and the proposed new mining extents (red lines). As can be seen, most of this new mining will occur directly under the Holfontein Stream and thus within the 50-year flood lines

In the following sections, it is assumed that mine water would be discharged directly into the Holfontein Stream from the Holfontein Shaft. It must be noted that this may not necessarily be the case (refer to Section 1.7.3).

7.1.3 The impact on the average base flow in the Holfontein Stream from groundwater discharged from the Holfontein Shaft

In Section 1.5.2.6 (Table 12) it was shown that the discharge of 7 Ml/day would increase the average base flow in the Holfontein Stream by between






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450 and 1 400%. This is a significant flow increase above the average monthly base flow in this stream. It was, however, also shown that the stream was capable of accommodating the peak discharge produced by a flood with a return period of 1 year without sustaining severe damage to the riverine environment. The calculated 1-year flood would in all likelihood produce a discharge in the Holfontein Stream of 703 Ml/day (albeit only for a few minutes, after which the discharge would begin to diminish). The sustained flow in the Holfontein Stream during the month with the highest flow (March), when the 7 Ml/day from the shaft is added to the base flow in the stream, will be ~8½ Ml/day, orders of magnitude lower than the discharge the 1-year flood would produce. However, where the peak discharge from a 1-year flood would only last for a few minutes, the discharge from the mine would be sustained more-or-less continuously and could lead to elevated erosion. However, the low fall and accompanying wide (but shallow) area of inundation would counter the effect of erosion. From AED's experience on other projects, where comparatively poor quality mine water was discharged into previously non-perennial streams, changing the non-perennial nature of a stream to a perennial stream, and also adding some nutrients to the stream (normally nitrogen compounds due to the explosives used underground) usually results in the proliferation of certain types of vegetation (bulrushes, reeds and other species that can grow in slightly saline mine water) within a year or two from when the discharge began. Although these species will proliferate and sometimes impede the flow of a river due to the dense nature of their growth, they will also counter erosion and the formation of channels in a watercourse. It would be essential to monitor the growth of aquatic vegetation, particularly at the inlets to culverts, where excessive vegetation would impede the flow of the stream. However, aquatic vegetation requires several years to establish and the Holfontein Mine will only operate for ~ 10 years. The Blesbokspruit is a good example of this phenomenon occurring, but over several decades.

7.1.4 The impact on the peak flow volumes in the Holfontein Stream should Holfontein Shaft water be discharged into this stream

In Section 1.5.2.5 (Graph 7 and Table 11), it was shown that an additional flow rate of 7 Ml/day would have a negligible effect on the expected peak flow that would result from a storm with a specific return period, falling over the catchment of the Holfontein Stream. The percentage change to the predicted peak flow for return periods ranging between 1 and 20 years would vary between 0.5% (for a flood with a return period of 1 year) and 0.06 % (for a flood with a return period of 20 years). These are insignificant percentages and thus, the alteration to the peak floods are of no concern.






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7.1.5 The impact of the groundwater discharged from the Holfontein Shaft on the water users at Welgedacht Smallholdings

In Section 4 it was shown that neither of the two culverts under the roads crossing the Holfontein Stream would be capable of handling anything greater than the base flow in the stream. Neither of the culverts under Carnation and Phlox Roads in Welgedacht SH are designed for any major storm and thus the discharge of water from the Holfontein Shaft could have a compounding effect, should mine water discharge coincide with any major storm event (not necessarily a 100-year storm, but any storm with a return period greater than ~4 years). Provided that mine water is discharged into the Holfontein Shaft directly from the Holfontein Mine (and not at one of the other alternative discharge points), it is recommended that NKGM increase the capacity of the culverts under Phlox and Carnation Roads (refer to Figure 18) to allow for at least the additional flow in the Holfontein Stream, but preferably for allowing the combined flow, during a storm with a 5-year (38.5 m³/s) or 10-year (51.5 m³/s) return. It is recommended that an additional series of culverts be placed alongside the existing culverts, if possible. Alternatively, an entirely new culvert must be constructed to replace the original one. It must also be noted that the haul route between Holfontein and the metallurgical plant at Modder East makes use of Carnation Road. If this road is damaged or flooded, it could also mean a loss of production for Holfontein Mine, as trucks would not be able to pass over this stream. All of the issues discussed in Sections 7.1.3 to 7.1.5 can be avoided if the recommendations on the water discharge options discussed in Section 1.7.3 is heeded. AED recommends discharging the mine water at a point in the Blesbokspruit directly opposite the Municipal WWTW.

7.1.6 The impact of the haul road crossing on the flow regime of the Blesbokspruit

The haul road will cross the Blesbokspruit at a pre-existing river crossing. This crossing cannot be referred to as a bridge, as it merely comprises of earth filling from the outer edges of riparian zone of the river, through the Blesbokspruit wetland, up to the actual stream channel, where the entire flow of the Blesbokspruit must pass through a 1-m pipe placed in the river channel and filled up to a level above the water surface. The earth filling not only impedes the flow of water in the Blesbokspruit and hinders the movement of migratory aquatic species up and down the river, but more importantly, the single pipe, without any in- or outlets, has lead to






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accelerated erosion and channel formation through the wetland downstream from the crossing. Purely from a hydrological point of view, channel formation through a wetland will lead to more flashy floods occurring in downstream reaches of the stream. Thus, where possible, channel formation through wetlands must be avoided and where they already exist due to anthropogenic interference with the wetland, they should be discouraged from increasing in magnitude. In the light of the above, it is essential that the promotion of any additional channel formation be avoided, by constructing proper in- and outlets to properly constructed (and adequately sized) culverts under the road. Particularly the outlet of a culvert system must be constructed in such a manner that the energy in the flowing water is dissipated across a wide area to prevent channel formation. In addition, the culvert system must be able to accommodate at least a pre-determined flow rate. To determine to what specifications the river crossing must be constructed, a 10-year flood, produced by a storm with a 10-year return period falling over the catchment of the Blesbokspruit upstream from the haul road crossing, was modelled. It was assumed that the Holfontein mining project would occur over an approximate 10-year period, and thus, it could be expected that the road crossing would either be overtopped at least once during the 10-year LoM period, or with a bit of luck, a 10-year storm would not occur during the life of the mine. With a catchment of 166 Km², a mean annual rainfall of 697.98 mm/a (quaternary catchment C21D), Veld Zone 4 (Grasslands of the interior plateau) in terms of the Midgley-classification (Midgley, 1972) and a time of concentration of 4 hours, a storm with a return period of 10 years would produce a peak discharge of 164.5 m³/s. If this discharge is compared to the discharges of 365.9 and 295.8 m³/s respectively for the 100- and 50-year floods, it might be assumed that the 10-year flood would produce a much narrower area of inundation than those of the two large floods. This assumption is unfortunately not correct, as the railway line bridge, with its long filled up approaches, crossing the Blesbokspruit diagonally immediately downstream from the haul road crossing, will produce a huge bridge backwater (essentially a dam) behind this railway line crossing during a flood. This dam formation is due to an inadequately sized opening through which the Blesbokspruit must flow and also due to the very low slope of the Blesbokspruit in that area. This bridge backwater effect is demonstrated clearly in Figure 20. What will actually happen during a 10-year flood is that the floodwaters will dam up against the railway line until it reaches the opening under the railway line where the haul road passes under this railway line. Then some of the






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water will flow through this opening and the 10-year flood elevation will not rise any further. Due to the low slope of the Blesbokspruit, the velocity of the floodwater in the stream just upstream from the haul road crossing will only be ~0.7 m/s in the centre (deepest part) of the Blesbokspruit during a 10-year flood. This velocity then progressively diminishes to zero as one moves laterally away from the centreline of the stream to the edges of the area of inundation. At the same time and for the same flood, the velocity under the railway line bridge will be ~2.7 m/s and the entire inlet opening will be underwater.

Figure 20: The 100-, 50- and 10-year flood lines of the reach of the Blesbokspruit upstream from the railway line crossing and including the haul road crossing of the Blesbokspruit

Thus, and although the 10-year area of inundation is wider than what would have been expected, during a 10-year flood, the velocity will not exceed 0.7 m/s, provided that the water is not channelled through a single culvert, as is the case with the railway line bridge further downstream. It is thus imperative that the haul road level be raised to an elevation of 1597.53 mamsl to ensure the road surface is above the 10-year flood elevation and that there are several smaller culverts spread across the width of the 10-year flood area






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of inundation which, cumulatively, would accommodate the discharge of 164.5 m³/s (i.e. the discharge of a 10-year flood) at a slope of only 0.000 858 7 m/m (i.e. a fall of 1:1 165). Each of these culvert outlets should be designed that the energy of the flowing water is dissipated where it leaves to downstream side of the culvert. This must be done to prevent channel formation.

7.1.7 The ability of the Holfontein Mine to separate "clean" and "dirty" water during a 50-year/24-hour flood event

The Holfontein Mine main shaft will be a comparatively small operation. Unlike stand-alone mineshafts, and apart from topsoil that is in any case non-polluting, this mine will not have to stockpile any mining-related material, such as waste rock or ore. Thus, there will be limited surfaces that could potentially pollute surface water run-off during a storm. In Section 1.5.1 it was shown that a 50-year/24-hour storm event would produce a run-off of 21.7 l/m² off natural grassland. By adjusting coefficient "C" in the normal rational formula, Q=CIA, new values were derived that reflected the actual run-off that could be expected off several other surfaces normally associated with mining. This resulted in Table 8 being produced, which shows the expected surface run-off from actual surfaces in the layout plan for the Holfontein Shaft. All surfaces that could produce polluted surface run-off will be connected via drains to the PCD in the northwestern corner of the fenced in shaft area. It was calculated that the PCD would hold 3 801 m³ of which 2 596 m³ would be usable storage capacity, i.e. the volume of the dam below 800mm below the spillway, while the combined surface run-off from contaminated areas at the shaft during a 50-year/24-hour storm event would amount to 2 400 m³ (refer to Table 8), thus the PCD is capable of accommodating the flow produced by this particular storm and still have an 80-mm emergency buffer below the spillway level. It is therefore important to empty the PCD as soon as possible after a rainstorm, to ensure that it would always have sufficient storage capacity to accommodate the flow off the contaminated areas during a 50-year/24-hour flood event. With the correct storm water drains installed and the PCD as it is presently designed, there should be no problem at the mine to separate "clean" from "dirty" water during a 50-year/24-hour storm. Water and environmental management at the new Holfontein project will be a far cry from the historic gold mining that occurred there in the 1930s. Refer to Photo 8, which is an aerial photograph taken in 1944, shortly after the mine ceased to operate. This photo demonstrates how mining was conducted in






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early gold mining days without any regard for water or environmental protection.

Photo 8: A historic photograph of the Holfontein Shaft area, taken during 1944, shortly after mining operations ceased at this shaft shows a total disregard for environmental protection by mining operations during the heydays of mining on the Witwatersrand

As far as the vent shaft is concerned, and once the sinking of the shaft has been completed, and given the fact that it will only be used for ventilation purposes and for emergency evacuation of mineworkers, it is unlikely that any contamination would emanate from this shaft. The only exception would be if water vapour condenses while it is drawn up the shaft. This condensate will then be contaminated with dust from the underground mine workings, with the residue of the combustion of diesel in the trackless haulages of the mine and with other compounds that may be found in a mineshaft. However, water usually only condenses when a ventilation shaft is deep. The Holfontein Vent Shaft is comparatively shallow and it is unlikely that large amounts of condensate would form during the updraft of air from the mine. However, if this does occur, an evaporation pond will be constructed. The sediment from this pond will be removed and sent to ME for processing, together with the ore produced at the main Holfontein shaft.






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7.2 Surface Water Quality of the Holfontein Stream

7.2.1 The impact of mining at Holfontein Shaft on the water quality in the Holfontein Stream

From the samples collected from the Holfontein Stream it is clear that the water in this stream is of a particularly high quality, given that it actually rises at a hazardous waste landfill site. This also indicates that water quality and water management is considered high on the list of priorities at this landfill site. The presence of a mineshaft, particularly a gold mine shaft, normally suggests that the water quality in the stream downstream from the shaft will deteriorate significantly, particularly when underground mine water is discharged into this stream. When referring to Photo 8, it is clear that previous mining at this shaft had no consideration of environmental management during its first "life" in the 1930s. However, the proposed mining at this shaft by NKGM will not be anything similar to the mining during the 1930s. As shown in Section 5.1.7, the PCD, which will be constructed in the northwestern corner of the fenced in area, is more than adequately sized to accommodate the surface run-off produced by a 50-year/24-hour storm event. Therefore no contaminated water will run off the mine surface to the Holfontein Stream. Likewise, the mine will be operated as a section of the ME Operations, with all services and support being provided by the ME Operations. Thus, there will be no waste rock dump, no ore stockpile, no gold plant, no workshops, or any other polluting items of infrastructure normally associated with gold mining. Thus, the pollution potential from surface sources at the Holfontein Mine is very limited.

7.2.2 The impact of the discharge of groundwater from the Holfontein Shaft on the water quality in the Holfontein Stream

Unlike the surface water run-off from the Holfontein Shaft, which is unlikely to have an impact on the water quality in the Holfontein Stream, water pumped from underground is likely to contain pollutants normally associated with gold mining on the Witwatersrand. These pollutants include sulphate (produced by the oxidation of pyrite, found in the ore body) in the form of sulphuric acid, calcium (and the associated total hardness caused by this metal) used in association with carbonate to neutralise the acidity in the water, uranium, which is toxic and its radioactive isotope, which could cause cancer over prolonged periods if the concentration is sufficiently high, and several other determinants (particularly metals such as arsenic, cobalt, chromium and nickel) that are sometimes associated with Witwatersrand gold mining and which would be solubilised under acidic conditions.






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Then there are the nitrogen compounds; ammonium, ammonia, nitrite and nitrate, all of which are directly associated with the explosives used underground to break rock. These compounds are highly soluble and will be found in the water pumped from underground at the Holfontein Shaft. As these nitrogen compounds are also plant nutrients, the sustained discharge of water containing elevated concentrations of nitrogen will also lead to the proliferation of algae and other aquatic plants, which, in turn, will alter the ecological and hydrological state of a stream. The water sampled from the Holfontein Shaft by Shango Solutions during 2014 (Handley, 2014), proved to be of a very high quality. In Section 2.4, it was shown that it is likely that water flow in the shaft occurred from the local groundwater aquifer towards the shaft, rather than vice versa. This would also explain the comparatively high water quality in a flooded Witwatersrand gold mining shaft. It is AED's contention, however, that this water quality will begin to deteriorate once pumping commences and would eventually be similar in quality to the water pumped from other mineshafts in the same area. Thus, in the end, water pumped from the mineshaft will have high sulphate concentrations, a low pH and would contain all the metals normally associated with gold mining. As the eventual water quality is presently not known, and the volume of 7 Ml/day is still just a calculated groundwater ingress estimate, the treatment options for this water are currently unknown. The Grootvlei Gold Mine was allowed to discharge up to 120 Ml of mine water daily into the Blesbokspruit for several decades. This water was treated using a "high density sludge" (HDS) treatment process and it could be argued that DWS might allow an effluent with an HDS plant effluent quality. HDS processing is a proven technology that has been in use in the mining industry since the 1980s. The process begins by mixing incoming effluent with a neutralising agent (lime) and recycled sludge from a clarifier/thickener unit. After neutralisation, this mixture is fed to the main lime reactor where a combination of aggressive aeration and high shear agitation ensures optimum process chemistry and clarifier performance. The discharge from the lime reactor is then treated with flocculent in the flocculation tank to promote precipitation and sent to the clarifier/thickener unit. The clarifier separates the treated effluent from the sludge, a portion of which is recycled to the head of the process, while the rest is waste (in the form of a slurry). The HDS process can reduce sulphate from several thousands of mg/l down to about 2 000 mg/l, or potentially 1 500 mg/l under very well controlled conditions. The sulphate is precipitated as gypsum (CaSO4). Most of the dissolved metals, including uranium, would also be co-precipitated during this process. However, to reduce the sulphate further would require additional treatment processes such as ion exchange or reverse osmosis.






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The other problem with treatment of mining water using HDS technology is that it produces a lime/gypsum sludge that does not dewater very well and which could pose a storage problem at Holfontein. At present it is not envisaged to dispose of this slurry on site. However, disposal at the Holfontein hazardous waste landfill site may also not be an option if the radioactivity (due to the uranium in the precipitate) exceeds the NNR Act's limits of 500 Bq/Kg. In this case, the sludge will be removed to ME for processing in the metallurgical plant and disposal onto the tailings dam, which is licensed in terms of the NNR Act.

7.3 Environmental Impacts during the Construction, Operation and Decommissioning Phases of the Holfontein Project

Mining took place at the Holfontein Mine during the 1930s and early 1940s, after which the shaft has been closed for about 75 years. Currently, the mine is flooded to an elevation of 1481 mamsl. The water level in the Blesbokspruit at the same latitude (i.e. where the N12 freeway crosses the Blesbokspruit) is at ~1577 mamsl. This means that the water level in the shaft is well below (~96 m below) the surface water level in the Blesbokspruit and thus also well below the assumed groundwater level in the same region. The life of mine (LoM) will consist of two years of construction and development (2019 to 2020), and 8 years of gold production (2021 to 2028). A further 6 months to a year is assumed for decommissioning and closure.

7.3.1 Construction/Recommissioning Phase

The Holfontein Shaft will be recommissioned. Access to the Main Reef will be through the existing Holfontein Shaft that was decommissioned in the early 1940s. In order to refurbish this shaft, the shaft will concurrently be dewatered and re-equipped. This process will require 20-24 months (2019 to 2020). Construction of associated site infrastructure will also occur concurrently. At the same time a new ventilation shaft will be sunk to intersect one of the existing haulages, constructed during the original era of mining at this shaft. This ventilation shaft will be equipped with up-draft fans as well as a small headgear and cage to evacuate miners during emergencies. From a hydrological and water quality perspective, the following issues will arise:

Unless water is discharged directly into the Holfontein Stream, the first item that must be constructed is the pipeline from the shaft to the discharge point for mine water.






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The shaft will then be dewatered. Although the shaft itself would contain a limited volume of water, it is uncertain exactly how much water will have to be pumped before the shaft is dry (in mining terms, "dry" means the shaft is accessible for mineworkers - not necessarily bone dry). Current available information indicates that discharge will occur at a rate of 1.2 l/s (0.104 Ml/day) during initial dewatering (2 years), and increasing to 83 l/s (7.17 Ml/day) at full production. The initial dewatering will occur at a comparatively slow rate, as the water will be lowered as the shaft is refurbished. There would not be any merit in dewatering too far ahead of the refurbishment down the shaft.

During this period comparatively good water will be discharged into the Holfontein Stream, or directly into the Blesbokspruit.

Old and corroded material, which could potentially contain uranium and other radioactive substances, will be hoisted to surface and stored in the salvage yard and/or lay down area. This area is fitted with drains that will direct run-off water to the PCD. When necessary the sediment intercepted by the PCD will be removed to ME.

During this period the water currently filling the shaft will gradually be replaced with water from the old haulages and stopes and the water quality is likely to begin to deteriorate (increasing in sulphate concentration). Although at water qualities as reported on by Shango Solutions (Handley, 2014), the water currently in the shaft can be discharged directly into the Holfontein Stream or Blesbokspruit untreated, at a certain point during the recommissioning stage, it would become necessary to commission the water treatment plant that will treat the underground water to meet the required standards specified by DWS in the mine's WUL.

Unless discharge occurs at one of the alternative discharge points, discussed in Section 1.7.3, the flow in the Holfontein Stream will be changed from being predominantly non-perennial in nature to being a perennial stream.

During this construction phase, the river crossing over the Blesbokspruit and its associated wetland will be upgraded (it will form part of the Mine's WUL), while the culverts under Carnation and Phlox Roads will be upgraded to accommodate at least the additional flow in the Holfontein Stream during a storm with a return period of 5 years (38.5 m³/s) or 10 years (51.5 m³/s), if water is indeed discharged into the Holfontein Stream at the mine.

7.3.2 Operational Phase

Once the shaft has been dewatered and refurbished with twin hoist headgear, the haulages will be developed (new haulages) or refurbished (existing haulages, depending what is actually found once the mine is dry) to accommodate trackless mining vehicles. Mining will be done using conventional narrow stoping methods. During this initial period, most rock material brought to surface will be waste rock, which will be loaded directly






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onto trucks and which will be hauled to the ME Operations along the haul road. Once actual production starts, ore hoisting will be limited to a 12-hour day shift to limit the noise associated with tipping of ore. Hoisting will take place 23 days a month, at 1 200 T/day. From a hydrological and water quality perspective, the following issues will arise:

The volume of water ingress into the mine will increase progressively, which will produce an ever-increasing volume being discharged into the Holfontein Stream or to one of the alternative discharge points in the Blesbokspruit. It is estimated that the discharge would reach a maximum of ~7 Ml/day, near the end of the LoM.

The mine-water treatment plant will begin to produce sludge, which will be disposed of at the Holfontein hazardous waste landfill site, provided it does not exceed the radiation clearance level for 238U (of 500 Bq/Kg) of

Section 2.1.1.1(b) of Reg. 388 (Govt. Gazette No. 28755 of 28 April 2006) promulgated i.t.o. The National Nuclear Regulator Act, 1999 (Act 47 of 1999)

(NNR Act). The same applies for 234U. The initially good water quality discharged into the Holfontein Stream,

or to one of the alternative discharge points in the Blesbokspruit, will deteriorate to a water high in sulphate, possibly in the range of 1 000 to 2 000 mg/l after treatment in the treatment plant.

Provided that water is indeed discharged into the Holfontein Stream and not piped or to one of the alternative discharge points in the Blesbokspruit, as discussed in Section 1.7.3, the character of the Holfontein Stream will continue to change from a bare, mostly non-perennial stream to an overgrown perennial stream, most likely with problems arising due to the reeds/bulrushes impeding the flow in the stream, towards the latter part of the LoM. It may be necessary to control the reed/bulrush growth at the inlets the main tarred road (named Pansy Rd in Welgedacht Smallholdings) immediately downstream from the mine, as well as the inlets to the two culverts at Carnation and Phlox Roads in Welgedacht SH. The proliferation of reeds/bulrushes will be due to the use of nitrogen-based explosives underground. The waste products, all still containing large amounts of nitrogen compounds, will readily dissolve in the mine water that will be pumped to surface and will be discharged into the Holfontein Stream.

During this 8-year period, the Holfontein Stream could experience a 10-year flood event, or more likely, a 5-year flood (refer to Graph 7 and Table 11 for flow rates). If such a flood occurs prior to the upgrading of the culverts, and provided the option to discharge directly into the Holfontein Stream at the mine is selected, it must be expected that damage would occur at some of the Welgedacht SH immediately upstream from the road crossings, due to the additional (albeit






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marginal) flow in the Holfontein Stream resulting from the Holfontein Mining operations. Issues relating to litigation and compensation may have to be considered by NKGM. For this reason it is imperative that the re-sizing of the culverts be carried out before the mine water is discharged into the Holfontein Stream. From a practical point of view, it would also make more sense to modify the culverts before the additional water is discharged into the stream. If one of the other discharge options were chosen, as discussed in Section 1.7.3, none of these issues would arise.

7.3.3 Decommissioning

After mining operations are completed, decommissioning will commence. Both shafts will be dismantled and the shaft openings will be capped. All surface infrastructure items will be dismantled and removed. This will include the PCD, which will be emptied after all other potentially polluting items are removed, and the sediment that has accumulated in this dam will be removed to either ME Operations or to the Holfontein hazardous waste landfill site, depending on the gold content in the sediment and whether the residue is radioactive or not (whether the radioactivity achieves clearance in terms of Section 2.1.1.1(b) of Reg. 388 (Govt. Gazette No. 28755 of 28 April 2006) of the

NNR Act. All disturbed areas will be ripped, covered with a layer of topsoil and returned as closely as possible to the present state. From a hydrological and water quality perspective, the following issues will arise:

A potential source of pollution will be removed from the catchment of the Holfontein Stream.

The flow in the Holfontein Stream will revert back to its natural state. Within a few years, the excessive vegetation growth in this stream will

gradually be replaced with vegetation similar to what is currently growing along the watercourse.

The mine will begin to flood and eventually, the water level will stabilise at roughly the same elevation it was before recommissioning of the mine began. This statement will have to be verified by the groundwater specialist, but all things being equal; there is no reason to assume otherwise. Thus, it is also likely that, if the water level stabilises at the same elevation it was prior to recommissioning of the mine (i.e. as it is at present), no decant would occur.

7.4 Quantitative Risk Assessment

Prime Resources advised/prescribed the quantitative risk assessment methodology by which potential impacts had to be evaluated / described. The quantitative environmental risk assessment was based on:






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Consequence of occurrence in terms of: o Nature of the impact (negative / positive); o Extent of the impact, either local, regional, national or across

international borders; o Duration of the impact, either short term (0-3 years), medium

term (4-8 years) or long-term (the impact will cease after the operational life of the activity) or permanent, where mitigation measures by natural processes or human intervention will not occur;

o Intensity of the impact, either being low, medium or high effect on the natural, cultural and social functions and processes;

Probability of occurrence which describes the likelihood of the impact

actually occurring and is indicated as: o Improbable, where the likelihood of the impact is very low; o Probable, where there is a distinct possibility of the impact to

occur; o Highly probable, where it very likely that the impact will occur; o Definite, where the impact will occur regardless any

management measure; In order to assess each of the factors for each impact the ranking scales below are used:

Magnitude (M) Duration (D)

10 – Very high (or unknown) 5 – Permanent

8 – High 4 – Long-term (ceases at end of operation)

6 – Moderate 3 – Medium-term (4-8 years)

4 – Low 2 – Short-term (0-3 years)

2 - Minor 1 - Immediate

Scale (S) Probability (P)

5 – International 5 – Definite (or unknown)

4 – National 4 – High probability

3 – Regional 3 – Medium probability

2 – Local 2 – Low probability

1 – Site 1 – Improbable

0 – None 0 – None

SIGNIFICANCE = (MAGNITUDE + DURATION + SCALE) x PROBABILITY

The maximum potential value for significance of an impact is 100 points. Environmental impacts are therefore rated as having a high, medium or low significance based on the following:

High environmental significance 60 – 100 points Medium environmental significance 30 – 59 points Low environmental significance 0 – 29 points

Management measures were identified to mitigate, prevent and /or reduce the risk.






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Significance was determined both pre-mitigation and post-mitigation. Tables 15 to 17 respectively contain evaluations for the Construction Phase, Operational Phase and Closure/Post-mining Phase. Square brackets “[ ]” in Tables 15 to 17 indicate lower rating values which were performed after considering the “Mitigation and Management Measures”.






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Table 15: Surface water impact assessment for the Construction Phase

No. Receptor /

Resource Process/Activity

Environmental

Impact

Impact

Effect

Magnitude

(M)

Duration

(D)

Scale

(S)

Probability

(P)

Significance Mitigation and

Management Measures

Impact Monitoring

Monitoring Timeframe for

Monitoring Ratin

g Value

14.1 Surface Water

General construction of site, incl. Main & Vent Shafts and all surface infrastructure, including a pipeline to the mine water discharge point (unless water is discharged directly into the Holfontein Stream

Surface vegetation will be removed from areas intended for surface infrastructure construction and area will be bare

If rainy season, siltation of Holfontein Stream could occur

Negative 2

[2]

2

[2]

1

[1]

2

[2]

Low

[Low]

10

[10]

Carry out construction during dry season if possible

Construct temporary berm between Main shaft and stream. No berm necessary at Vent Shaft Ensure that water treatment plant is operational before dewatering commences

During rainy season, inspect berm after thunderstorms. Repair if necessary

Until site has been constructed and clean and dirty drain separation has been implemented

14.2 Surface Water Dewatering of shaft. Water discharged into Holfontein Stream or to one of the alternate discharge points

Initially water quality will be good, but will deteriorate as deeper water is drawn in from the mine workings

Negative 4

[4]

2

[2]

2

[1]

5

[5]

Med

[Med]

40

[35]

Ensure water treatment plant is on line to meet DWS WUL requirements Ensure that all relevant culverts have been upgraded to accommodate larger volumes of water

Measure EC of water discharged into stream daily When EC begins to deteriorate, bring water treatment plant on line Treated water must meet DWS WUL conditions Implement surface water monitoring programme. Continue to monitor water quality pre and post treatment

Until discharge of water is terminated






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No. Receptor /


Environmental

Impact

Impact

Effect

Magnitude

(M)

Duration

(D)

Scale

(S)

Probability

(P)


Management Measures

Impact Monitoring


Monitoring Ratin

g Value

14.3 Surface Water

Handling of old and corroded material recovered from shaft

Material may contain contaminants and potentially radioactive elements

Negative

6 [2]

2 [2]

2 [2]

3 [3]

Med [Low]

30 [18]

Ensure that lay down area/salvage yard, where material is stored, is fitted with drains to the PCD Remove material as soon as possible to an area of safety off the Holfontein Site. Have radiation officer declare material safe for removal off site Ensure that PCD is constructed prior to other infrastructure and ensure that construction of drains to PCD is completed before refurbishment of shaft begins

Radiation Measurement of all material brought from underground by mine's appointed Radiation Officer

Until all scrap is removed from shaft and shaft is refurbished






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Table 16: Surface water impact assessment for the Operational Phase

No. Receptor /


Environmental

Impact

Impact

Effect

Magnitude

(M)

Duration

(D)

Scale

(S)

Probability

(P)


Management Measures

Impact Monitoring


Monitoring Rating Value

15.1 Surface Water

Development of U/G mine and haulages to accommodate trackless mining. Large volumes of rock produced underground, loaded on trucks and removed from site to NKGM

Significant loading of trucks and removal of waste rock to rock dump at ME Operations

Potential for spillage into Holfontein Stream and Blesbokspruit

Negative 2 [2]

2 [2]

2 [2]

2 [1]

Low [Low]

12 [6]

Ensure that haul road surface is always in good condition - inspect regularly - repair frequently Haul trucks will be covered with a tarpaulin Ensure that watercourse crossings are maintained in good condition

Frequent road and culvert inspections

Life of mine

15.2 Surface water Discharging of a progressively increasing volume of water into Holfontein Stream or into the Blesbokspruit with potentially decreasing water quality.

Volume of water ingress into mine increases. Water discharged into Holfontein Stream increases

Water quality in discharged water decreases (depending on water treatment process and conditions of WUL. Potential of contaminating groundwater (boreholes) from surface stream

Negative 10 [6]

3 [3]

2 [2]

2 [1]

Med [Low]

30 [11]

Ensure water treatment plant operates efficiently

Ensure that WUL water quality conditions are met or exceeded

Inspect stream and note channel formation. Mitigate if needed

Daily monitoring of EC of discharged water

Monthly monitoring of water quality at sampling points

Construct gabion structures if excessive erosion becomes a problem in the Holfontein Stream provided that his option is chosen

Life of Mine

15.3 Surface water Water treatment plant begins producing by-product (in the case of HDS plant, large volumes

Potential spillage along route

Storage on site until load warrants

Negative 2 [2]

3 [3]

1 [1]

4 [4]

Low 24 [24]

Ensure spillages of sludge does not occur by properly training of responsible personnel

Daily visual inspection by responsible person for water treatment plant to ensure that is not routed to storm

As long as water treatment plant is in operation during operational phase






Created on 06/08/2015 07:45:00

No. Receptor /


Environmental

Impact

Impact

Effect

Magnitude

(M)

Duration

(D)

Scale

(S)

Probability

(P)


Management Measures

Impact Monitoring



of liquid sludge that will be trucked (tanker truck) away from site to a safe disposal site

removal Ensure that plant is working optimally

water drain or even into PCD

15.4 Surface Water Discharge of water high in Nitrogen compounds into Holfontein Stream, or Blesbokspruit, due to the use of explosives underground

Nitrogen compounds are plant nutrients - results in excessive growth of aquatic vegetation with the resulting impeding of water flow in stream, particularly at culverts. If discharge into the Blesbokspruit at the WWTW, this issue would be mitigated by dilution from the sewage effluent

Negative

6

[6]

4

[4]

2

[2]

4

[2]

Med

[Low]

48

[24]

Inspect culverts monthly during summer months and implement cutting of reeds/vegetation at entrances and outlets of culverts when needed

Inspect river and particularly culverts monthly

Life of Mine

15.5 Surface Water Occurrence of a flood event (with return periods of 2, 5, 10 or 20-years) in the Holfontein Stream - note that this is a natural environmental occurrence

Flooding at the Welgedacht SH may be to a slightly higher elevation than natural flood. May result in damage and associated litigation.

Negative

6 [4]

3 [3]

2 [2]

5 [5]

Med [Med]

55 [45]

Ensure that culverts at Welgedacht SH are increased in size before water is discharged from the mine Ensure culverts are kept free of blockages (incl. vegetation) Ensure residents in Welgedacht SH are aware of natural flooding dangers and dangers due to poor construction of railway line

Inspect river and potential flood damage immediately after flood occurs. This is imperative for the mine.

Take as many photographs as is necessary to record water levels accurately, particularly if water levels are indicated on walls or structures that can be used as benchmarks, particularly id a scale

Life of mine






Created on 06/08/2015 07:45:00

No. Receptor /


Environmental

Impact

Impact

Effect

Magnitude

(M)

Duration

(D)

Scale

(S)

Probability

(P)


Management Measures

Impact Monitoring



embankment through Welgedacht SH Ensure residents are made aware of culvert resizing by mine Discharge mine water to one of the alternate discharge points in the Blesbokspruit

(ruler/tape measure) is included in the photograph

Table 17: Surface water impact assessment for the Closure and Post-Closure Phases

No. Receptor /


Environmental

Impact

Impact

Effect

Magnitude

(M)

Duration

(D)

Scale

(S)

Probability

(P)


Management Measures

Impact Monitoring

Monitoring

Time

Frame for


6.1 Surface Water A potential source of pollution will be removed from the catchment of the Holfontein Stream, and/or from the Blesbokspruit The discharge of mine water into the Holfontein Stream will cease

Hydrology of the Holfontein Stream will return to pre mining Aquatic vegetation which has established in the Holfontein Stream will gradually make place for the vegetation type that existed in the stream prior to mining

Positive 4 [4]

5 [5]

2 [2]

5 [5]

Med [Med]

55 [55]

None required Continue to carry out water quality sampling until no more mining impact is noticeable in analyses results (when water quality returns to baseline water quality - as recorded in this report)

Until water quality returns to baseline conditions






Created on 06/08/2015 07:45:00

No. Receptor /


Environmental

Impact

Impact

Effect

Magnitude

(M)

Duration

(D)

Scale

(S)

Probability

(P)


Management Measures

Impact Monitoring

Monitoring

Time

Frame for


16.2 Surface water Demolition of surface infrastructure at both shafts. Sealing of shaft entrances

Potential for spillages of hazardous materials

Negative 2 [2]

2 [2]

1 [1]

2 [1]

Low [Low]

10 [5]

Sequence of demolition must ensure that polluting infrastructure is removed before surface drains and PCD are removed PCD and drains to PCD must be one of the last items to be removed Sludge accumulated in PCD must be and adequately disposed

None required other than proper site management during demolition phase

Until all items are removed and area is returned to a more natural state

16.2 Surface water Water decant from shaft after shaft is flooded

Unlikely environmental impact unless large water strike occurs during mining

Negative 6 [6]

5 [5]

2 [2]

1 [1]

Low [Low]

13 [3]

Low probability of occurrence Ongoing monitoring of water level in both shafts

Monitor water levels in main and vent shafts until stabilised

Until water levels in both shafts stabilises






8. Conclusions The surface water and hydrology environmental impact assessment has shown that, although there were some issues that must be managed and mitigated, in general, there were no fatal flaws in the recommissioning of the old Holfontein Shaft. Given the dwindling mining contribution to the South African GDP and the comparatively low impact this mine will have on the aquatic and hydrological environment, it is AED's contention that the mine should be allowed to remove the remaining gold resources by making use of a pre-existing mine shaft, i.e. the mine would have a minimal impact on the aquatic environment as no new shaft would be sunk.






9. References Bauer, S. W., Midgley, D. C.: (1974): ‘A Simple Procedure for Synthesizing Direct Run-off Hydrographs’ CSIR/University of the Witwatersrand Report No. 1/74 Botha, L.: (2012): 'Gold One International Modder East Mine; Groundwater Impact Assessment for EIA/EMP Amendment'. Groundwater Square Consulting Groundwater Specialists Botha, L.: (2015): 'Gold One International Modder East Mine, Holfontein, Groundwater Impact Assessment (Draft Report)" Groundwater Square Consulting Groundwater Specialists Botha, L.: (2015): 'Gold One International Modder East Mine, Holfontein, Groundwater Impact Assessment" Groundwater Square Consulting Groundwater Specialists Dept. of Water Affairs (1986). ‘Management of the Water Resources of the Republic of South Africa’. Department of Water Affairs and Forestry. (1996): ‘South African Water Quality Guidelines, Volume 1: Domestic Use’. Second Edition SEF (2015): 'Proposed Holfontein Project Aquatic Impact Assessment'. Strategic Environmental Focus Report No 506295 Handley, R.: (2014): "In-situ water sampling of the Houtpoort No. 3 and Holfontein Shafts'. Shango Solutions Report No. SS0471/14. Hornberger, G. M.; Raffensperger, J. P.; Wilberg, P. L.; Eshleman, K. N. (1998): ‘Elements of Physical Hydrology’. John Hopkins University Press Krige, W. G.; (2012): ‘Surface Water and Hydrological Aspects pertaining to the proposed alterations to the New Kleinfontein Goldmine (Pty) Ltd, located on the Remaining Extent of the farm Cloverfield 75 IR, Ekurhuleni, Gauteng Province, South Africa' African Environmental Development Report No. AED0223/2012. Middleton, B. J.; Bailey, A. K. (2005): ‘Water Resources of South Africa, 2005 (WR2005) Version 1’. Water Research Commission Project No. K5/1491 Midgley, D. C.: (1972): ‘Design Flood Determination in South Africa’. CSIR/University of the Witwatersrand Report No. 1/72






Midgley, D. C.; Pitman, W, V.; Middleton, B. J. (1994): ‘Surface Water Resources of South Africa’. Water Research Commission Report No. 298/94 SANS 241, Edition 1 (2011): ‘South African National Standard for Drinking Water. South African Bureau of Standards’






Appendix 1: Holfontein Stream and Blesbokspruit Flood Lines CAD files

Please double click on the above icons to open the AutoCAD DXF files

Appendix 2: Water Quality Analyses Report

Please double click on the above icon to open the PDF file

Complied and Approved by: Quality managerGarfield Krige 17795-20150304 Biomonitoring Page 1 (of 3) Revision Status:0003 Efective date: 2012-12-01

ENVIRONMENTAL MONITORING

COOKE 1 RESIDENCES CC CK97/47253/23(OFF R559) 34 LARK CRESCENTCOOKE 1 GREENHILLS RANDFONTEIN RANDFONTEIN

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African Environmental DevelopmentRent-en-Dal 1751 Tel. No.: (011) 956-6537No 129 Malmani Road Fax. No.:Sterkfontein Country Estates e-mail: [email protected]

Date: 19-Mar-2015Ref: 17795/20150304

Attention: Garfield Krige

Sample identification :

Type of sample:Number of samples:Condition of sample(s):

Sampled By: Garfield Sampling procedure: N/A

Date received: 4-Mar-2015

4Acceptable

DD SCIENCE cc

Water Samples

TEST REPORT

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Test Results

Sample ID Units Method Holfontein 01 Holfontein Holfontein 03 Holfontein 04Blesbokspruit

Date Sampled 2015/03/03 2015/03/03 2015/03/03 2015/03/03Lab ID 17795/1 17795/2 17795/3 17795/4

pH @25ºC M001 9.1 7.8 7.4 7.7Conductivity mS/m @25ºC M002 71 49 27 27

Total Hardness mg/l CaCO3 Calculated from Ca and Mg Analysis 102 167 84 109Total Alkalinity mg/l CaCO3 M015 120 194 90 83

Sulphate mg/l M020 60 <40 (6) <40 (9) <40 (37)Nitrate mg/l N M021 <0.5 <0.5 <0.5 1.5

Chloride mg/l M016 94 35 18 <5.0Ammonia mg/l N M093 3.5 2.7 2.2 1.8Calcium mg/l M009 21 42 20 32

Magnesium mg/l M010 12 15 8.2 7.1Sodium mg/l M012 83 37 16 7.2

Potassium mg/l M011 17 9.3 3.9 5.2Uranium µg/l ICPMS 1.0 0.4 0.2 0.5

Aluminium µg/l ICPMS 70 26 28 369Antimony µg/l ICPMS 0.4 0.05 0.1 0.3

Barium µg/l ICPMS 22 61 100 59Beryllium µg/l ICPMS 0.03 0.03 0.02 0.02Bismith µg/l ICPMS 0.002 0.001 0.002 0.003

Cadmium µg/l ICPMS 0.01 0.03 0.02 0.003Chromium µg/l ICPMS 0.1 <0.001 0.1 1.8

Cobalt µg/l ICPMS 0.3 0.3 1.4 0.2Lanthanum µg/l ICPMS 0.04 0.01 0.04 0.1

Lithium µg/l ICPMS 0.7 1.0 0.4 0.9Platinum µg/l ICPMS 0.1 <0.001 0.001 0.002Selenium µg/l ICPMS 0.4 0.5 <0.001 0.4Tellurium µg/l ICPMS 0.4 0.05 0.05 0.3Thallium µg/l ICPMS 0.01 0.01 0.01 0.03

Tin µg/l ICPMS 0.01 0.01 0.01 0.02Titanium µg/l ICPMS 0.05 <0.001 0.9 9.7

Vanadium µg/l ICPMS 0.7 0.1 0.1 1.6Manganese µg/l ICPMS 5.9 156 1544 22

Iron µg/l ICPMS 60 49 190 174Asernic µg/l ICPMS 1.8 0.6 <0.001 0.4Nickel µg/l ICPMS 2.7 0.9 1.8 1.8Zinc µg/l ICPMS 0.7 5.7 1.7 2.8

Copper µg/l ICPMS 0.7 5.7 1.7 2.8Lead µg/l ICPMS 0.1 0.3 0.3 0.3

Mercury µg/l ICPMS 0.9 0.8 0.7 0.9Molybdenum µg/l ICPMS 0.6 0.1 0.4 1.1


Opinions and interpretations (if any):

Compiled andapproved by: Alfred Molubi (Technical Signatory)

Date of issue: 19-Mar-2015Reviewed by: D. Dorling (Executive Manager)

Please note: 1. Results are strictly confidential and will not be disclosed to any third person.2. Results relate only to the samples tested;3. This report shall not be reproduced, except in full, without the written approval of DD Science cc4. While every effort is made to provide a service of the highest quality, the liability of DD Science ccshall not extend beyond the cost of services rendered;5. The resposibility of any work subcontracted rest with DD Science.6. Samples will be disposed of two weeks after the date of issue of this report, unless otherwise instructed by the client.

Documents

This report may be cited as follows - Squarespacestatic1.squarespace.com/static/54f70cebe4b0d3690344a50b/...This report may be cited as follows: Krige W. G. (2015): 'Surface Water