Floodline Determination for the Resource and Reserve ...

Floodline Determination for the Resource

and Reserve Drilling Project at the

Dwarsrivier Chrome Mine

Project Number:

ENG004

Prepared for:

EnviroGistics (Pty) Ltd

P.O. Box 22014, Helderkruin, 1733

Email: [email protected]

Tel: 082 412 1799

Fax: 086 551 5233

Compiled by:

Hydrospatial (Pty) Ltd

17 Sonop Place, Randpark, 2194

Email: [email protected]

Tel: 084 441 9539

July 2018

mailto:[email protected]

Floodline Determination for the Resource and Reserve Drilling Project at the Dwarsrivier Chrome Mine

ENG004

i July 2018

DOCUMENT CONTROL

Project Name Floodline Determination for the Resource and Reserve Drilling Project at the

Dwarsrivier Chrome Mine

Report Type Floodline Determination

Client EnviroGistics (Pty) Ltd

Project Number ENG004

Report Number 02

Report Status Final draft

Submission Date 26 July 2018

Author Andy Pirie (Pr.Sci.Nat.)

Author Signature


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ii July 2018

TABLE OF CONTENTS

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

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

1.1 Project Location ...................................................................................................... 1

1.2 Legal Requirements ................................................................................................ 3

1.2.1 National Water Act (Act No. 36 of 1998) .......................................................... 3

1.2.2 Government Notice 704 ................................................................................... 3

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

3 METHODOLOGY AND DATA SOURCES ..................................................................... 3

3.1 Site Visits ................................................................................................................ 3

3.2 Elevation Data ........................................................................................................ 4

3.3 Land Cover and Soils .............................................................................................. 4

3.4 Mannings n Roughness Coefficients ....................................................................... 4

3.5 Peak Flow Calculations ........................................................................................... 4

3.6 Software Choice ..................................................................................................... 5

3.7 Hydraulic Model Setup ............................................................................................ 6

4 ASSUMPTIONS AND LIMITATIONS ............................................................................ 6

5 CATCHMENT CHARACTERISTICS AND PEAK FLOWS ............................................ 6

6 RESULTS AND DISCUSSION ...................................................................................... 9

6.1 Assessment of the Possible Drainage Line near the Proposed Truck Parking

Facility (Option 1) .............................................................................................................. 9

6.2 Drilling Project ....................................................................................................... 16

7 CONCLUSIONS AND RECOMMENDATIONS ............................................................ 24

8 REFERENCES ............................................................................................................ 25

LIST OF TABLES

Table 4-1: Catchment characteristics, Rational Method parameters and calculated peak

flows ..................................................................................................................................... 8


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LIST OF FIGURES

Figure 1-1: Location of the Mine ............................................................................................ 2

Figure 5-1: Catchments and general topography .................................................................. 7

Figure 6-1: Cross-section A................................................................................................... 9

Figure 6-2: Cross-section B................................................................................................. 10

Figure 6-3: Cross-section C ................................................................................................ 10

Figure 6-4: Cross-section D ................................................................................................ 10

Figure 6-5: Drainage line cross-sections near the proposed truck parking option 1 facility .. 11

Figure 6-6: Road blocking the clean cut-off trench .............................................................. 12

Figure 6-7: Blocked culvert near the fence below the Sekhukhune road ............................. 12

Figure 6-8: Catchments 1 and 2 .......................................................................................... 13

Figure 6-9: Catchment 1 floodlines and 100 m drainage line buffer ..................................... 14

Figure 6-10: Catchment 2 floodlines and 100 m drainage line buffer ................................... 15

Figure 6-11: Catchment 3 floodlines and 100 m buffer ........................................................ 17

Figure 6-12: Catchment 4, 5, 6 and 7 floodlines and 100 m buffer ...................................... 18

Figure 6-13: Catchment 8, 9, 10 and 11 floodlines and 100 m buffer .................................. 19

Figure 6-14: Catchment 12, 13 and 14 floodlines and 100 m buffer .................................... 20

Figure 6-15: Catchment 15 floodlines and 100 m buffer ...................................................... 21

Figure 6-16: Catchment 16 and 17 floodlines and 100 m buffer .......................................... 22

Figure 6-17: Catchment 18 floodlines and 100 m buffer ...................................................... 23


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iv July 2018

EXECUTIVE SUMMARY

Hydrospatial (Pty) Ltd (hereafter Hydrospatial) was appointed by EnviroGistics (Pty) Ltd

(hereafter EnviroGistics) to undertake a floodline determination for the Dwarsrivier Chrome

Mine (hereafter the Mine) Resource and Reserve Drilling Project (hereafter the Drilling

Project). In addition to the above, Hydrospatial was further requested to assess the area

between the discard dump and old Tailings Storage Facility (TSF), as the Mine is

considering a truck parking facility near to a drainage line that was previously diverted for

open pit operations, and which is currently still in place.

The area between the old TSF and discard dump, where the truck parking option 1 is

proposed, was thoroughly assessed during a site visit. A remnant drainage line was noted in

the area, that consisted of a shallow channel directly south-east of the discard dump, but

was noted to be more defined further downstream. In order to determine whether water

would flow down the drainage line, the topography of the area was assessed, to determine if

there would be any contributing catchment area. Two contributing catchments were

delineated; catchment 1 took the clean cut-off trench that diverts water around the discard

dump into consideration, while catchment 2 ignored the trench. The 1:50 and 1:100 year

floodlines indicated that the truck parking option 1 falls outside of the floodlines in both

instances (catchment 1 and 2), but within the 100 m buffer of the drainage line.

The 1:50 and 1:100 year floodlines were determined for the drainage lines that intersect the

proposed Drilling Plan. A number of drilling targets and access roads are located within the

floodlines and 100 m buffer.

The following is recommended:

■ The clean cut-off trench upslope of truck parking option 1 is upgraded. This includes

unlocking the culvert near the Sekhukhune road, which may require the installation of

a new culvert, due to its poor condition. It is recommended that should a new culvert

be considered, that it is sized correctly to convey the 1:50 year runoff, as required by

the GN704 Regulations. It is further recommended that a culvert is considered where

the road has blocked the trench. Lastly, the sizing of the clean cut-off trench should

be checked, to ensure that it complies with GN704;

■ Truck parking option 1 falls outside of the 1:100 year floodlines, but within a 100 m

horizontal distance of the drainage line. It is recommended that a GN704 exemption

from Regulation 4 (a) and (b) is obtained;

■ The proposed drilling holes and access roads that fall within the 1:50 year floodlines,

and within a 100 m horizontal distance of the drainage lines, are exempted from

GN704 regulations 4 (a) and 4 (b);

■ In order to minimise the impacts of the drilling sites located within the floodlines, it is

proposed that they are only accessed during the dry season; and


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■ A 100 m buffer has been placed around the Richmond dam, however, this should be

confirmed with the Department of Water and Sanitation.


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1 July 2018

1 INTRODUCTION AND BACKGROUND

Hydrospatial (Pty) Ltd (hereafter Hydrospatial) was appointed by EnviroGistics (Pty) Ltd

(hereafter EnviroGistics) to undertake a floodline determination for the Dwarsrivier Chrome

Mine (hereafter the Mine) Resource and Reserve Drilling Project (hereafter the Drilling

Project). In addition to the above, Hydrospatial was further requested to assess the area

between the discard dump and old Tailings Storage Facility (TSF), as the Mine is

considering a truck parking facility near to a drainage line that was previously diverted for

open pit operations, and which is currently still in place.

The Drilling Project involves the construction of access roads, drilling pads and the removal

of vegetation. The drill pads are proposed to be 20 metres (m) by 20 m (400 m²), and will

comprise of the drill site and a portable sump for the storage of dirty water from drilling

activities. Dirty water collected by the portal sump, will be disposed of in a licenced facility.

Access roads to drill sites will be 6 m wide, and will be temporary in nature. Temporary

offices may be erected if and when required. Small scale diesel/lubrication/oil storage may

be required for the drill rigs. The exploration activities are planned over the Dwarsrivier Mine

Mining Rights area, however, this will extend onto the Two Rivers Platinum Mines Surface

Rights area, which includes the Two Rivers Platinum Mine Plant, as well as the TSF. For the

TSF, the exploration programme will allow for a 100 m buffer. Where mine infrastructure is

present, consultation with the landowner will be undertaken and drilling will only be

conducted in approved areas and in line with the landowners’ rules and requirements. Since

the mine is located within a mountainous area, various drainage lines are present.

The 1:50 and 1:100 year floodlines for the Dwars Rivier, Klein Dwars Rivier and

Springkaanspruit, were previously determined for the Mine (Krige, 2009). However, a

number of ephemeral (only flowing in response to high rainfall) drainage lines indicated on

the 1:50 000 topographical maps, were not determined, which are located in close proximity

to the proposed exploration drilling holes and access roads.

The purpose of this report is to summarise the floodline determinations undertaken for the

Drilling Project, as well as the assessment of the potential drainage line near the proposed

truck parking option 1.

1.1 Project Location

The Mine is situated approximately 60 km northwest of Lydenburg, 25 km south of

Steelpoort and 63 km northeast of Roossenekal in the Limpopo Province (Error! Reference

source not found.).


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Figure 1-1: Location of the Mine


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1.2 Legal Requirements

The following legal requirements are applicable to this study:

1.2.1 National Water Act (Act No. 36 of 1998)

According to section 21 of the National Water Act (Act No. 36 of 1998) (hereafter NWA), the

following sections are relevant in terms of water uses –

(c) Impeding or diverting the flow of water in a watercourse; and

(i) Altering the bed, banks, course or characteristics of a watercourse.

1.2.2 Government Notice 704

According to Regulation 4 of Government Notice 704 (hereafter GN704), promulgated in

terms the NWA, no person in control of a mine or activity may –

(a) Locate or place any residue deposit, dam, reservoir, together with any associated

structure or any other facility within the 1:100 year floodline or within a horizontal distance of

100 metres from any watercourse or estuary, borehole or well, excluding boreholes or wells

drilled specifically to monitor the pollution of groundwater, or on water-logged ground, or on

ground likely to become water-logged, undermined, unstable or cracked; and

(b) Carry on any underground or opencast mining, prospecting or any other operation or

activity under or within the 1:50 year floodline or within a horizontal distance of 100 m from

any watercourse or estuary, whichever is the greatest.

Exemption from the above requirements may be applied for, in terms of Regulation 3 of

GN704.

2 SCOPE OF WORK

The scope of work for the study included the following:

■ Determine the 1:50 and 1:100 year floodlines for drainage lines indicated on the 1:50

000 topographical maps, that intersect the proposed resource drilling plan; and

■ Assess the area between the discard dump and old TSF near the proposed truck

parking option 1, to determine if a drainage line exists in the vicinity.

3 METHODOLOGY AND DATA SOURCES

3.1 Site Visits

Two site visits were undertaken on 11 May and 22 June 2018. The purpose of the site visits

was to assess the catchment characteristics, channels and floodplains of the drainage lines


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under consideration. A thorough walkthrough of the area between the old TSF and discard

dump was conducted.

3.2 Elevation Data

Accurate, detailed and up-to-date elevation data is a critical component for accurate floodline

modelling. Elevation data from the following sources was used for modelling purposes:

■ 5 m contour interval elevation data obtained from the Mine from the file: Master Plan

2018 - Existing Infrastructure.dgn. Although not ideal in terms of the course scale

contour interval resolution, as well as being outdated, this was the best available

elevation data covering the Drilling Project; and

■ 1 m contour elevation data obtained from the Mine for the area between the old TSF

and discard dump. This area was surveyed between 21 to 23 February 2018 by Trail

Surveys, and was used to model the floodlines for this area.

3.3 Land Cover and Soils

Land cover and soil data is used in the calculation of the peak flows. Land cover data was

assessed using Google Earth imagery, as well as the 2013 – 2014 South African National

Land-Cover Dataset (Geoterraimage, 2015).

An understanding of the soil types of the area was obtained from the 2010 Environmental

Management Programme Report (EMP) for the Mine. Soil data was further obtained from the

land type and capability dataset from the Agricultural Resource Council – Institute for Soil,

Climate and Water (ARC-ISCW).

3.4 Mannings n Roughness Coefficients

The Manning’s n roughness coefficients are values that are used to model the channel and

adjacent floodplains resistance to flow. The Mannings roughness was assessed during the

site visits. The channels of the drainage lines in the area were noted to be generally shallow

and not well defined, and consisted of fairly dense vegetation. Similarly, the adjacent

floodplains also consisted of dense vegetation. Based on these observations, a Mannings n

roughness coefficient of 0.1 was assigned to the channels and adjacent floodplain areas.

3.5 Peak Flow Calculations

The Rational Method is a hydrological method that was used to estimate the 1:50 and 1:100

year peak flows. It is based on the following equation:

𝑄𝑇 =𝐶 𝐼 𝐴

3.6

where:


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5 July 2018

QT = Peak flow for a recurrence interval e.g. a 1:100 year flood (m³/s)

C = Runoff coefficient (dimensionless)

I = Average rainfall intensity over the catchment (mm/hour)

A = Catchment area contributing to the peak flow (km²)

3.6 = Conversion factor

The runoff coefficient “C” is calculated from the physical characteristics of the contributing

catchment. These include the vegetation type, slope, soil permeability, and land use

characteristics.

The average rainfall intensity “I” was calculated from the gridded storm rainfall depths

obtained from Smithers and Schulze (2002), and is equal to the time of concentration (Tc).

The Tc is the amount of time it takes for water to travel from the hydraulically most remote

point of the catchment, to the catchment outlet. It is essentially the amount of time for runoff

in the catchment to contribute to the peak flow.

The contributing catchment area “A” was calculated by delineating a catchment for the peak

flow points. The 5 m contours obtained from the Mine as well as the 1:50 000 topographical

contours were used to delineate the contributing catchments.

A Microsoft Excel spreadsheet (Gericke and du Plessis, 2013) was used to calculate the

peak flows based on the South African National Roads Agency Limited (SANRAL)

procedure.

The Rational Method is based on the following key assumptions:

■ Rainfall has a uniform area distribution across the total contributing catchment;

■ Rainfall has a uniform time distribution for at least a duration equal to the Tc;

■ The peak discharge occurs when the total catchment contributes to the flow

occurring at the end of the critical storm duration, or Tc;

■ The runoff coefficient “C” remains constant for the storm duration, or Tc; and

■ The return period of the peak flow is the same as that of the rainfall intensity.

3.6 Software Choice

The following software’s were used:

■ ArcMap 10.2 is a Geographical Information System (GIS) software programme used

to view, edit, create and analyse geospatial data. ArcMap was used to view spatial

data and to create maps. Its extension 3D Analyst was used for terrain modelling

purposes, for converting the elevation data into a DEM grid format;

■ HEC-GeoRAS utilises the ArcMap environment and is used for the preparation of

geometric data (cross-sections, river profile, banks and flow paths) for input into the


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6 July 2018

HEC-RAS hydraulic model. It is further used in post processing to import HEC-RAS

results back into ArcMap, to perform flood inundation mapping; and

■ HEC-RAS 4.1 (Brunner, 2010) was used to perform hydraulic modelling. HEC-RAS is

a hydraulic programme used to perform one-dimensional hydraulic calculations for a

range of applications, from a single watercourse to a full network of natural or

constructed channels.

3.7 Hydraulic Model Setup

Development of the hydraulic model included the following steps:

■ Preparation of geometric data (cross-sections, stream centre lines, bank lines and

flow paths) in HEC-GeoRAS;

■ Importing of geometric data into HEC-RAS;

■ HEC-RAS setup for the Manning’s n roughness coefficient values at cross-sections,

entering peak flows, and entering upstream and downstream slope boundary

conditions for normal depth calculations;

■ Performing steady, mixed flow (combination of subcritical, supercritical, hydraulic

jumps and drawdowns) hydraulic modelling within HEC-RAS to generate flood water

levels at cross-sections; and

■ Importing flood level elevations at cross-sections into HEC-GeoRAS to perform

floodplain delineations.

4 ASSUMPTIONS AND LIMITATIONS

The following are key assumptions and limitations:

■ Due to the use of coarse resolution 5 m contour data for modelling, the determined

floodlines must only to be used for environmental and indicative purposes, to provide

a broad estimate of the 1:50 and 1:100 year flood levels. They cannot be used for

engineering design purposes; and

■ Calibration of the hydrological and hydraulic models was not possible. Conservative

guideline values for parameters have been used based on site observations. This is

a standard approach for determining indicative floodlines.

5 CATCHMENT CHARACTERISTICS AND PEAK FLOWS

An overview of the catchments delineated to calculate the flood peaks is indicated on Figure

5-1. The catchment characteristic, Rational Method parameters, and calculated peak flows

are summarised in Table 5-1.


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Figure 5-1: Catchments and general topography


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Table 5-1: Catchment characteristics, Rational Method parameters and calculated peak flows

Catchment MAP (mm)

Catchment Area (km²)

Longest Water- course

(km)

Average Slope of Longest Water- course (m/m)

1:50 Year Runoff

Coefficient

1:100 Year Runoff

Coefficient

Tc (hrs)

1:50 Year

Rainfall Intensity (mm/h)

1:100 Year

Rainfall Intensity (mm/h)

Peak Flow

Method

1:50 Year Peak Flow (m³/s)

1:100 Year Peak Flow (m³/s)

Catchment 1 571 0.06 0.4 0.046 0.309 0.373 0.29 143.4 162.4 Rational 0.7 1.0



















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6 RESULTS AND DISCUSSION

6.1 Assessment of the Possible Drainage Line near the Proposed Truck

Parking Facility (Option 1)

During the site visit, a remnant drainage line/ditch was noted between the old TSF and

discard dump. This drainage line was previously diverted to prevent flooding of open pit

operations, which have since been rehabilitated. The diversion is still currently in place

(Figure 6-8), and diverts runoff away from the North Return Water Dam, and into the

Springkaanspruit.

The drainage line near to the proposed truck parking option 1 was confirmed by assessing

the 1 m contour survey data. A number of cross-sections were drawn through the drainage

line as indicated on Figure 6-5. The upper section of the drainage channel, directly to the

south-east and south of the discard dump, is shallow and not well defined (Figure 6-1 and

Figure 6-2), but becomes more defined and prominent towards the lower sections (Figure

6-3 and Figure 6-4).

Figure 6-1: Cross-section A

Cross-Section A

Horizontal Distance (m)

50454035302520151050

ma

msl

932.3

932.2

932.1

932

931.9

931.8

931.7

931.6


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Figure 6-2: Cross-section B

Figure 6-3: Cross-section C

Figure 6-4: Cross-section D

Cross-Section B


26252423222120191817161514131211109876543210

mam

sl

928.8

928.6

928.4

928.2

928

927.8

927.6

Cross-Section C


35302520151050

mam

sl

926

925.8

925.6

925.4

925.2

925

924.8

924.6

924.4

924.2

Cross-Section D


56545250484644424038363432302826242220181614121086420

ma

msl

920.6

920.4

920.2

920

919.8

919.6

919.4

919.2

919

918.8


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Figure 6-5: Drainage line cross-sections near the proposed truck parking option 1

facility


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In order to determine whether water would flow down the drainage line, the topography of

the area was assessed, to determine if there would be any contributing catchment area.

Catchments 1 and 2 were delineated as indicated on Figure 6-8. This was done as a clean

cut-off trench was noted upstream of the drainage line, which diverts runoff around the

discard dump (Figure 6-6). However, the cut-off trench was noted to be degraded, as it was

blocked by a road (Figure 6-6), and was further noted to be blocked at a culvert near the

fence below the Sekhukhune road (Figure 6-7). Catchment 1 considers the upslope clean

water cut-off trench to be fully operational, diverting upslope runoff around the discard dump.

Catchment 2 considers the cut-off trench to be degraded (as noted on the site visit), allowing

upslope runoff to pass into the drainage ditch between the old TSF and discard dump. The

1:50 and 1:100 year floodlines for catchment 1 and 2 are indicated on Figure 6-9 and Figure

6-10.

Figure 6-6: Road blocking the clean cut-off trench

Figure 6-7: Blocked culvert near the fence below the Sekhukhune road


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Figure 6-8: Catchments 1 and 2


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Figure 6-9: Catchment 1 floodlines and 100 m drainage line buffer


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Figure 6-10: Catchment 2 floodlines and 100 m drainage line buffer


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As observed from Figure 6-9 and Figure 6-10, the truck parking option 1 falls outside of the

floodlines, but within the 100 m buffer of the drainage line. It is therefore unlikely that the

proposed truck parking will disturb the drainage line or be at risk of flooding. However, the

elevated area (approximately 1.5 m to 3 m elevation difference) on which the truck parking is

proposed, should be kept in place, as it provides important elevation for the left bank of the

drainage line. Due to the truck parking facility being located within the 100 m buffer of the

drainage line, it is likely that a GN704 exemption from Regulation 4 (a) and (b) will be

required.

6.2 Drilling Project

The 1:50 and 1:100 year floodlines and 100 m buffer of drainage lines intersecting the

Drilling Project are indicated on Figure 6-11, Figure 6-12, Figure 6-13, Figure 6-14, Figure

6-15, Figure 6-16 and Figure 6-17 below. A number of drilling targets and access roads are

located within the floodlines and 100 m buffer. As mentioned under section 1.2, no mining

activities may take place within the floodlines or 100 m buffer of watercourses, without

obtaining exemption from GN704. Furthermore, the drill sites and access roads may

potentially disturb drainage lines, triggering a water use in terms of section 21 (c) and (i) of

the NWA. In order to minimise any impact on the drainage lines, it is recommended that they

are only accessed during the dry season.


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Figure 6-11: Catchment 3 floodlines and 100 m buffer


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Figure 6-12: Catchment 4, 5, 6 and 7 floodlines and 100 m buffer


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Figure 6-13: Catchment 8, 9, 10 and 11 floodlines and 100 m buffer


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Figure 6-14: Catchment 12, 13 and 14 floodlines and 100 m buffer


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Figure 6-16: Catchment 16 and 17 floodlines and 100 m buffer


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24 July 2018

7 CONCLUSIONS AND RECOMMENDATIONS

Hydrospatial was appointed to determine the 1:50 and 1:100 year floodlines for drainage

lines intersecting the Mines proposed Drilling Project. In addition to the above, Hydrospatial

was further requested to assess the area where the truck parking option 1 facility is

proposed, to determine whether a drainage line is present.

The area between the old TSF and discard dump, where the truck parking option 1 is

proposed, was thoroughly assessed during a site visit. A remnant drainage line was noted in

the area, that consisted of a shallow channel directly south-east of the discard dump, but

was noted to be more defined further downstream. Two contributing catchments were

delineated; catchment 1 took the clean cut-off trench into consideration, while catchment 2

ignored the trench. The 1:50 and 1:100 year floodlines indicated that the truck parking option

1 falls outside of the floodlines in both instances (catchment 1 and 2), but within the 100 m

buffer of the drainage line.

The 1:50 and 1:100 year floodlines were determined for the drainage lines that intersect the

proposed Drilling Plan. A number of drilling targets and access roads are located within the

floodlines and 100 m buffer.

The following is recommended:

■ The clean cut-off trench upslope of truck parking option 1 is upgraded. This includes

unlocking the culvert near the Sekhukhune road, which may require the installation of

a new culvert, due to its poor condition. It is recommended that should a new culvert

be considered, that it is sized correctly to convey the 1:50 year runoff, as required by

the GN704 Regulations. It is further recommended that a culvert is considered where

the road has blocked the trench. Lastly, the sizing of the clean cut-off trench should

be checked, to ensure that it complies with GN704;

■ Truck parking option 1 falls outside of the 1:100 year floodlines, but within a 100 m

horizontal distance of the drainage line. It is recommended that a GN704 exemption

from Regulation 4 (a) and (b) is obtained;

■ The proposed drilling holes and access roads that fall within the 1:50 year floodlines,

and within a 100 m horizontal distance of the drainage lines, are exempted from

GN704 regulations 4 (a) and 4 (b);

■ In order to minimise the impacts of the drilling sites located within the floodlines, it is

proposed that they are only accessed during the dry season; and

■ A 100 m buffer has been placed around the Richmond dam, however, this should be

confirmed with the Department of Water and Sanitation.


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8 REFERENCES

Brunner G.W. 2010. HEC-RAS – River Analysis System Hydraulic Reference Manual, US

Army Corps of Engineers Hydrologic Engineering Center (HEC).

Geoterraimage. 2015. The 2013 – 2014 South African National Land-Cover Dataset. Data

User Report and MetaData.

Gericke O.J. and du Plessis J.A. 2013. Development of a Customised Design Flood

Estimation Tool to Estimate Floods in Gauged and Ungauged Catchments. Water SA Vol.

39 No. 1 January 2013.

Land Type Survey Staff. 1972 - 2006. Land types of South Africa; Digital Map (1:250 000

scale) and Soil Inventory Database. Pretoria: ARC-Instatute for Soil, Climate, and Water.

Smithers J.C. and Schulze R.E. 2002. Design Rainfall and Flood Estimation in South Africa.

WRC Project No. K5/1060.

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