Cygnus Coal Mine Surface Water Specialist Study · • Separation of clean and dirty water streams and the release and containment of each stream respectively by constructing diversion

Cygnus Coal Mine – Surface Water Specialist Study

Report Prepared for

Universal Coal Development V (Pty) Ltd

Report Number 535300/Surface Water/RevA

Report Prepared by

April 2019

SRK Consulting: Project No: 535300 – Cygnus Surface Water Specialist Study Page i

MALE/SHEP 535300_Cygnus_Surface_Water_20190803_Final_Draft August 2019

Cygnus Coal Mine – Surface Water Specialist Study

Universal Coal Development V (Pty) Ltd

SRK Consulting (South Africa) (Pty) Ltd 265 Oxford Rd Illovo 2196 Johannesburg South Africa

e-mail: [email protected] website: www.srk.co.za

Tel: +27 (0) 11 441 1111 Fax: +27 (0) 11 880 8086

SRK Project Number 535300

April 2019

Compiled by: Peer Reviewed by:

Oliver Malete, Pr. Sci. Nat. Senior Hydrologist

Peter Shepherd, Pr. Sci. Nat. Partner

Email: [email protected] [email protected]

Authors:

O. Malete; P. Shepherd

http://www.srk.co.za/

mailto:[email protected]

SRK Consulting: Project No: 535300 – Cygnus Surface Water Specialist Study Page ii


Executive Summary

SRK Consulting Limited, (SRK) has been appointed by Universal Coal Development V (Pty) Ltd

(Universal Coal) to undertake the surface water specialist study to support the authorisation

application. The CCM is located in the Limpopo Province, some 120 km to the north of Polokwane and

to the north east of Vetfontein Farm.

Principal objectives

The objectives of the surface water study are to conduct a:

• Baseline study;

• Stormwater management plan;

• Water balance; and

• Impacts assessment.

Work programme

The work programme included:

• Site visit in June 2018;

• Updating the surface water hydrology for the site;

• Sizing of clean and dirty water stormwater channels; and

• Preparation of water balance scenarios

Conclusions and Recommendations

The surface water specialist study provides an indication of the steps and processes required in order

to meet the Regulation 704 criteria in terms of the National Water Act (Act No. 36 of 1998). These

include the following have been addressed:

• Separation of clean and dirty water streams and the release and containment of each stream respectively by constructing diversion berms and canals;

• Assessment of the impact of MAR changes on the local and quaternary catchment level

• Operating water balance for the mine, especially the Opencast Pit

• Groundwater collected in the sump of the opencast pit, which requires containment, treatment and or use, where possible;

• Constructing five culverts at various locations around the mine along the haul and access roads to route water efficiently back into the environment

The opencast pit requires a clean water cut off canal which will discharge the water to the west and

east as it straddles a high point in the middle of the canal.

The nature of a pit excavation may generate dirty water and cause it to flow into the natural

environment. A sump has been proposed for the pit as a means of creating a point from which to pump

the water out to a suitable containment and treatment location.

The rainfall and storm water within the buildings and workshop areas will result in increased peak flows

of the local catchment but any effluent generated within workshop areas should be controlled and

managed using localised sumps at various isolated areas.

The effects of mining activity on the catchment MAR in which all infrastructure are located, will be a

reduction a reduction of MAR of 43 641 m3 per annum (0.5%) on a local scale and 0.04% on a

SRK Consulting: Project No: 535300 – Cygnus Surface Water Specialist Study Page iii


quaternary catchment scale. With the mining activity located about 3 km away, this further lowers the

likelihood of negative impacts on the nearest surface water resource, the Brakrivier.

The project area is located in a very dry region of the Water Management Area resulting in a reduced

to absence of surface runoff for the majority of the year. As a result, the mine is likely to experience a

deficit in surface water supply resulting in an exclusive use of groundwater for the operations. The

foregoing ultimately results in surface water quality changes in the environment being very low.

The key impact assessment results are provided below.

Access Roads

Type of Impact

POTENTIAL IMPACT DESCRIPTION IN TERMS OF ENVIRONMENTAL ASPECTS

ENVIRONMENTAL SIGNIFICANCE BEFORE

MITIGATION IMPACT

MANAGEMENT ACTIONS

(PROPOSED MITIGATION MEASURES)

IMPACT MANAGEMENT OUTCOME

(ENVIRONMENTAL SIGNIFICANCE AFTER

MITIGATION) degree of mitigation

(%)

Significance (Degree to

which impact may cause

irreplaceable loss of

resources)

Significance Rating


which impact may

cause irreplaceable

loss of resources)

Significance Rating

Pre-Construction Phase

Direct Increased solids transport due to clearing/grubbing

30 Medium

Low

Construct in dry season and install silt bunds

20 Low 33

Indirect Increased runoff requiring retention on site

24 Low

Limit footprint and install retardation structures

16 Low 33

Direct Accidental hazardous substance spillages during construction phase

42 Medium

High Operate using best practices

24 Low 43

Construction Phase

Direct Impeding flow while under construction

30 Medium

Low

Construct in dry season.

20 Low 33

Protect with gabions & mattresses.

Remove litter & debris to stop blocking.

Direct

Accidental spillages of hazardous substances from construction vehicles used during construction of the crossings.

64 Medium

High

Control site access;

30 Medium

Low 53

Control refueling areas;

Restrict vehicular access to stream;

Clean spillages immediately they occur and remediate as necessary using spill kits.

Direct Contamination of runoff by poor materials/waste handling practices

35 Medium

Low

Park vehicles on hard standing with sump; 25 Low 29 Store hydrocarbons and other

SRK Consulting: Project No: 535300 – Cygnus Surface Water Specialist Study Page iv


Type of Impact



MITIGATION IMPACT

MANAGEMENT ACTIONS

(PROPOSED MITIGATION MEASURES)



MITIGATION) degree of mitigation

(%)


which impact may cause

irreplaceable loss of

resources)

Significance Rating


which impact may

cause irreplaceable

loss of resources)

Significance Rating

contaminants responsibly;

Bund fuel storage areas;

Store and dispose of waste responsibly.

Direct Debris from poor handling of materials and/or waste blocking watercourse

30 Medium

Low Operate using best practices

25 Low 17

Operational Phase

Direct Debris from upstream blocking watercourse at pipes/canals/culverts

49 Medium

High Operate using best practices

30 Medium

Low 39

Closure/Rehabilitation Phase

Direct Debris blocking watercourses if road continues to be used by the community.

49 Medium

High

Community needs to remove litter & debris to prevent blocking.

25 Low 49

Direct Impeding flow while under demolition

28 Medium

Low

Demolish infrastructure as far as possible in the dry season

20 Low 29

Direct Increased turbidity due to demolition.

36 Medium

Low

Demolish during dry season, limit the disturbed footprint.

20 Low 44

Direct

Accidental spillages of hazardous substances from construction vehicles used during demolition.

36 Medium

Low

Operate using best practices and clean spillages immediately they occur and remediate as necessary using spill kits.

24 Low 33

Post-Closure Phase

Direct Flooding caused by extreme rainfall event

35 Medium

Low

Warning signs to discourage crossing if pipes/culverts are submerged.

25 Low 29

Direct Damage to the crossings themselves

35 Medium

Low

Regular periodic inspections by successor in title and remediation as necessary.

20 Low 43

Opencast Pit and Plant Area

SRK Consulting: Project No: 535300 – Cygnus Surface Water Specialist Study Page v


Type of Impact



MITIGATION

IMPACT MANAGEMENT ACTIONS (PROPOSED

MITIGATION MEASURES)



MITIGATION)

degree of mitigation

(%)


which impact may

cause irreplaceable

loss of resources)

Significance Rating


which impact may

cause irreplaceable

loss of resources)

Significance Rating


Direct Water runoff requiring retention on site

15 Low Construct in dry season;

9 Low 40 Limit footprint.


36 Medium

Low Operate using best practices 24 Low 33

Construction Phase

Direct Impeding flow while under construction

28 Medium

Low

Construct in dry season and

20 Low 29

protect with gabions & mattresses and

remove litter & debris to stop blocking.

Direct

Accidental spillages of hazardous substances from construction vehicles used during construction of the crossings.

35 Medium

Low


25 Low 29



Clean spillages immediately they occur and remediate as necessary.


35 Medium

Low

Park vehicles on hard standing with sump;

24 Low 31

Store hydrocarbons and other contaminants responsibly;



Indirect Separate clean and dirty water streams

27 Medium

Low Construct diversion drains timeously

21 Low 22

Operational Phase

Indirect Pump failure will result in dirty water accumulation in the pit

30 Medium

Low

Undertake regular structural inspections of pumps and pipes exiting pit. Ensure groundwater investigation is done to understand groundwater levels.

20 Low 33

Direct Reduction in catchment Mean Annual Runoff

54 Medium

High

Minimise dirty water areas requiring containment as far as practically possible

25 Low 54

Direct Spilling of the pollution control dam

54 Medium

High

Maintain stormwater levels as close to empty as possible by using it for dust suppression

21 Low 61

Indirect High rate of ground water ingress

33 Medium

Low

Implement recommendations from groundwater study with regards to pumping and dewatering

24 Low 27


SRK Consulting: Project No: 535300 – Cygnus Surface Water Specialist Study Page vi


Type of Impact



MITIGATION





MITIGATION)


(%)


which impact may

cause irreplaceable

loss of resources)

Significance Rating


which impact may

cause irreplaceable

loss of resources)

Significance Rating

Direct Pit reaching capacity and overflowing to the environment.

40 Medium

High

Understand groundwater in the area and optimise mine planning activities

24 Low 40

Post-Closure Phase

Indirect Water quality changes downstream

40 Medium

High

Maintain stormwater collection system and monitoring. Consider an treatment effluent treatment plant if decanting is envisaged from the groundwater study

15 Low 63

SRK Consulting: Project No: 535300 – Cygnus Surface Water Specialist Study Page vii


Table of Contents

Executive Summary ..................................................................................................................................... ii

List of Abbreviations .................................................................................................................................... ix

1 Introduction .................................................................................................................. 1

2 Scope of Work .............................................................................................................. 1

3 Study Area .................................................................................................................... 2

3.1 Location ............................................................................................................................................... 2

3.2 Topography ......................................................................................................................................... 2

3.3 General description of the Limpopo Water Management Area .......................................................... 2

4 Climate and water quality ............................................................................................ 8

4.1.1 Evaporation ............................................................................................................................. 8

4.1.2 Rainfall..................................................................................................................................... 9

4.1.3 Water quality ......................................................................................................................... 10

5 Design rainfall depths ................................................................................................ 10

6 Stormwater Management Plan .................................................................................. 10

6.1 Proposed Mine Infrastructure ............................................................................................................ 11

6.2 Regional catchment delineation ........................................................................................................ 11

6.3 Mean annual runoff ........................................................................................................................... 14

6.4 Modelling ........................................................................................................................................... 15

6.4.1 Stormwater catchment delineation ........................................................................................ 15

6.4.2 Peak flows ............................................................................................................................. 16

6.4.3 Clean water management ..................................................................................................... 17

6.4.4 Dirty water management ....................................................................................................... 17

7 Water Balance ............................................................................................................. 21

7.1 Methodology ...................................................................................................................................... 21

8 Surface Water Impact Assessment ........................................................................... 23

8.1 Impact Assessment Methodology ..................................................................................................... 23

8.2 Activities to be rated .......................................................................................................................... 24

8.3 Project activities with potential to impact surface water resources ................................................... 24

8.4 Impacts associated with all activities ................................................................................................ 25

8.4.1 Pre-construction - site clearing and grubbing of the footprint areas ..................................... 25

8.4.2 Impacts during closure/rehabilitation ..................................................................................... 26

8.4.3 Post-closure .......................................................................................................................... 26

8.5 Impacts associated with the pit, plant area and associated infrastructure (e.g. pipelines, stormwater management) .................................................................................................................................... 26

8.5.1 Construction of the pit and associated infrastructure (access roads, pipelines) ................... 26

8.5.2 Operation of the Opencast Pit and Plant Area ...................................................................... 27

SRK Consulting: Project No: 535300 – Cygnus Surface Water Specialist Study Page viii


8.5.3 Operation of the buildings and workshop areas .................................................................... 27

9 Conclusions and Recommendations ........................................................................ 32

10 References .................................................................................................................. 34

Appendices ...................................................................................................................... 35

Appendix A: Wet and Dry Seasons Water Balance .................................................... 36

List of Tables Table 4-1: Average monthly evaporation (mm) .................................................................................................. 8

Table 5-1: Design rainfall depth for 24 hour period (SRK, 2018) ..................................................................... 10

Table 6-1: Catchment parameters for the local catchments ............................................................................. 11

Table 6-2: Natural MAR (from WR2012) and loss of MAR due to dirty water containment ............................. 14

Table 6-3: Natural MAR (from WR2012) and increase of MAR due to building constructions ........................ 14

Table 6-4: Quaternary natural MAR (from WR2012) and net loss of MAR due to dirty water containment .... 15

Table 6-5: Clean and dirty water sub-catchments within the proposed mine ................................................... 15

Table 6-6: PCSWMM method peak flows for each sub-catchment .................................................................. 16

Table 6-7: Peak flows comparison between the pre- and post-development scenarios .................................. 16

Table 6-8: Dirty water stormflow volume ..................................................................................................... 18

Table 6-9: Clean and dirty water channel arrangement and hydraulic properties for the 1 in 50 year design storm .......................................................................................................................................... 19

Table 6-10: Culvert arrangement and hydraulic properties .............................................................................. 19

Table 7-1: Key parameters used for the water balance ................................................................................... 21

Table 8-1: Cygnus Project Activities ................................................................................................................. 24

Table 8-2: Impact assessment for the access roads ........................................................................................ 28

Table 8-3: Impact assessment for the opencast pit and plant area ................................................................. 30

List of Figures Figure 3-1: Locality map of the proposed Cygnus Coal Mine ............................................................................ 6

Figure 3-2: Location of Cygnus within Limpopo River Catchment WMA 1 ........................................................ 7

Figure 4-1: Total and mean annual rainfall for the years 1923 to 1999 ............................................................. 9

Figure 4-2: Mean monthly rainfall for the period 1923 to 1999........................................................................... 9

Figure 6-1: Proposed site infrastructure ........................................................................................................... 12

Figure 6-2: Cygnus local catchments in relation to quaternary catchments ..................................................... 13

Figure 6-3: Proposed stormwater management plan for Cygnus Coal Mine ................................................... 20

Figure 7-1: Annual average water balance for the proposed Cygnus Coal Mine............................................. 22

SRK Consulting: Project No: 535300 – Cygnus Surface Water Specialist Study Page ix


List of Abbreviations

DWA Department of Water Affairs

DWAF Department of Water Affairs and Forestry

DWS Department of Water and Sanitation

EMP Environmental Management Plan

MRPDA Mineral and Petroleum Resources Development Act

NEMA National Environmental Management Act

NWA National Water Act

PCD Pollution Control Dam

SWD Storm Water Dam

SWMP Storm Water Management Plan

WMA Water Management Area

WULA Water Use Licence Application

SRK Consulting: Project No: 535300 – Cygnus Surface Water Specialist Study Page 1


1 Introduction

SRK Consulting was appointment by Universal Coal Development V (Pty) Ltd (UCDV) to undertake

environmental studies and associated authorisation application processes at the proposed Cygnus

Coal Mine (CCM). The CCM is located in the Limpopo Province, some 120 km to the north of

Polokwane and to the north east of Vetfontein Farm.

SRK Consulting (South Africa) (Pty) Ltd (SRK Consulting) was appointed by UCDV as the independent

environmental consultants to undertake the integrated EA/WML process. As part of this process, a

surface water specialist study is required to support the application.

This report outlines the hydrological baseline assessment, including the stormwater and water balance

for the proposed CCM.

2 Scope of Work

The scope of work for the investigation at CCM included the following:

• Baseline study

o Define and limit the boundaries and scale of the project, with respect to surface water (i.e. prepare surface water baseline);

o undertake an assessment of existing baseline data and supporting information;

o The baseline will be established during this task to develop a hydrological baseline with respect to water chemistry (quality) and quantity (flow), including the generation of flow statistics.

o Identify the major water courses within the area and estimate the catchment areas and hydrological parameters based on the site visit and contours/topography as supplied by the client;

o Estimate the Mean Annual Rainfall based on the rainfall available for the site. This will be estimated using a monthly Rainfall /Runoff model;

o The evaporation data will be estimated from the A-Pan data for stations near the area as supplied by the client or local metrological stations; and

o The Flood volumes for the identified catchments will be estimated using the SCS method.

o Calculate the impact of the mine on flood peaks and naturalised runoff

• Stormwater management plan

o Determination of catchment characteristics (catchment boundaries, water bodies, slope and drainage directions).

o Determination of impact on Mean Annual Runoff (MAR).

o Determination of storm water flows (m3/s) and volumes (m3) for the 1:50 and the 1:100 year return period event for the clean and dirty water areas.

o Determination of longer duration storm events for the purposes of storm water containment.

o Delineation of clean and dirty water areas on a drawing.

o Confirmation of the indicated placement of berms, channels and pollution control dams (PCD) to divert clean water around the dirty water areas as well as infrastructure required for the dirty water system, in line with Regulation 704 of the National Water Act (Act No. 36 of 1998) (NWA).

o Development of a plan/map for water diversion berms and conveyances for infrastructure; and

o Layout of the stormwater management plan.

• Water balance

o Annual average, wet and dry scenarios.



o Determination of water requirements for any excess water that will need to be absorbed into the mine.

• Reporting and Impact assessment

o All surface water impacts will be described and mitigation measures will then be proposed as normally required for the Environmental Impact Assessment/Environmental Management Plan (EIA/EMP), for the construction, operation, decommissioning and post closure phases.

o During this phase, refinements will be made to the stormwater management plan to improve the mitigation measures.

o The water balance will assist this phase by quantifying impacts and effects of the mitigation measures (where data are available).

3 Study Area

3.1 Location

The Project is located in the Limpopo Province, some 120 km to the north of Polokwane and to the

north east of Vetfontein Farm. The Project may be reached via an all-weather gravel road that

branches off from the tar road (road R584) between all days and Waterpoort. The Project Area is ~ 50

km by road from all days and 30 km by road from Waterpoort. The nearest sizeable town is Makhado

some 80 km by road to the southeast. The nearest accessible railway siding is at Waterpoort, ~ 30 km

southeast.

The location of the mine relative to the town of Waterpoort and its positioning in South Africa is shown

in Figure 3-1. A layout of the proposed site infrastructure is also indicated.

3.2 Topography

Although the catchment lies at a quaternary catchment divide, it consists of moderately hilly to

predominantly flat areas. The proposed Cygnus Coal Mine (CCM) is bordered by a small tributary of

the Sand River, Brakrivier, in the northern, flowing in a westerly direction, away from the DWM. No

other significant and defined water courses are to be found in close proximity to DWM and CCM.

3.3 General description of the Limpopo Water Management Area

Cygnus Coal Mine and its mining boundary is situated in Quaternary catchments A72B and A71J in

the Limpopo Water Management Area (WMA), WMA1, which is situated in the northern part of South

Africa, in the Limpopo Province. It is hydrologically associated with Sand River and all flows from the

site drain towards to Brakrivier, a non-perennial tributary of the Sand River. The Sand River, a tributary

of the Limpopo river, confluence with the Limpopo River, approximately 9 km east of Musina and 17

km downstream of Beitbridge.

The Limpopo River, formed by the confluence of both the Marico and Crocodile Rivers, originates in

the south west along the Botswana and South Africa borders approximately 70 km north west of

Thabazimbi.

The region is semi-arid, with economic activity mainly centred around livestock farming and irrigation,

together with increasing mining operations. Approximately 760 rural communities are scattered

throughout the water management area, with little local economic activity to support these population

concentrations. The WMA consists of a number of catchments which are mostly independent of each

other. The main catchments are the Matlabas, Mokolo, Lephalale, Mogalakwena, Nzhelele, and Sand,

where the project area is located.



Figure 3-1: Locality map of the proposed Cygnus Coal Mine



Figure 3-2: Location of Cygnus within Limpopo River Catchment WMA 1



4 Climate and water quality

Climate over the Limpopo WMA is temperate with frost occurring in winter, and is generally semi-arid.

The Mean Annual Precipitation (MAP) in the WMA ranges widely, with rainfall ranging from as little as

200 mm/annum in the north to over 1 200 mm/annum in the Soutpansberg mountains. In general

rainfall decreases from the south to the north, with the lowest rainfall occurring in the Limpopo valley

in the north-east of the WMA. The potential evaporation, which can be as high as 1 950 mm per year,

is well in excess of the rainfall.

The mean annual temperature of the Limpopo WMA ranges from 16° in the south to 22° in the north,

where the project area is located, with an average of 20° for the WMA as a whole. The average

maximum monthly temperature is 30° in the month of January, while the average minimum monthly

temperature is 4° in the month of July (DWAF, 2004).

Frost seldom occurs with the average number of frost days per year amounting to about 3 days that

is experienced mainly in the southern and western areas (DWAF, 2003).

Surface water quality within the project area is predominantly affected negatively during the rainy

seasons due to the very dry and arid nature of the region. This impact emanates predominantly from

the irrigation return flows from neighbouring agricultural lands.

4.1.1 Evaporation

The mean annual gross evaporation (as measured by Symons pan) ranges between 1 600 mm in the

southern region to 2 200 mm in the northern regions. The site evaporation character lies in the upper

levels of this range.

The monthly evaporation is presented in Table 4-1 (WR2012)

Table 4-1: Average monthly evaporation (mm)

Months Average Monthly Evaporation

Jan 203

Feb 166

Mar 166

Apr 135

May 128

Jun 105

Jul 119

Aug 145

Sep 176

Oct 204

Nov 196

Dec 208

Total 1950

High levels of evaporation mean that the soil dries up quickly reducing the amount of water available

for plant uptake meaning that crops become more prone to drought. Dryland subsistence farming is

generally not viable given the variable rainfall, high evaporation and high evapotranspiration (LEDET,

2015). Evaporation is highest during the rainfall season, and it significantly reduces effective rainfall,

runoff, soil infiltration and groundwater recharge. The Evaporative Demand in Limpopo ranges from



about 2 mm to 5 mm per day (ARC, 2015) and the project site demand more than likely lies in the

upper range of above 5mm/day.

4.1.2 Rainfall

Rainfall data was obtained from the Bandur weather station 0765007W. The Bandur data comprised

of 98 years of daily rainfall data (1903-2000) which was truncated to 77 years to obtain a period from

January 1923 to December 1999 due to data paucity. A long record of rainfall (>30 years) is required

to reliably assess statistical characteristics of the local rainfall therefore the combined rainfall record

is of sufficient length. Annual rainfall monitored between 1923 and 1999 was found to vary average

228 mm per annum with a range of between 51 mm and 525 mm (see Figure 4-1). The average

monthly rainfall variation is shown in Figure 4-2. The greatest proportion of rainfall occurs between

November and March and the least between May and September. Review of rainfall data presented

as Figure 4-1 suggests that between 1964 and 1981 rainfall followed a nine year cycle between periods

of high and low rainfall.

CYGNUS UNVERSAL COAL TOTAL AND MEAN ANNUAL RAINFALL FOR THE YEARS 1923 TO 1999

Project No. 535300

Figure 4-1: Total and mean annual rainfall for the years 1923 to 1999

CYGNUS UNVERSAL COAL MEAN MONTHLY RAINFALL FOR THE PERIOD 1923 TO 1999

Project No. 535300

Figure 4-2: Mean monthly rainfall for the period 1923 to 1999

0

100

200

300

400

500

600

Rai

nfa

ll (m

m)

Annual Rain Average 5-Year Annual Moving Average

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

0765007W 11.73 35.58 36.78 42.46 44.43 23.75 18.42 5.18 1.50 2.69 1.10 4.88

0.00

10.00

20.00

30.00

40.00

50.00

Mo

nth

ly R

ain

fall

(mm

)

MAP 228 mm



4.1.3 Water quality

The closest river or dam water quality sites recorded on the Department of Water Sanitation (DWS)

Resource Quality Information Services (RQIS) are situated approximately 20km upstream of the site

(A7H10 - Waterpoort 695 MS on Sand River) and 40 km downstream of the site (A7R1 - Dr Neethling

Dam on Sand River/Voorburg). No regional water quality site occurs within the Brakrivier catchment

and the Brakrivier was dry during the site visit. With this data, only the regional water quality status

could be inferred.

The Sand Key Area is by far the driest of all the Key Areas in the WMA, with a unit runoff of only 1

mm/a (DWAF, 2004), implying that surface water quality loads are very low throughout much of the

hydrological year.

Mining is an important economic driver in the Sand River catchment, comprising , silicon and diamond

mines and a platinum smelter. The introduction of a coal mine within the catchment will contribute to

a higher waste loading profile into the Sand River relative to the other commodities. This pollutant

loading is likely to occur via non-point source pollutant transport processes through a dry tributary such

as the Brakrivier during storm events. As a result, the cumulative water quality impacts to the surface

water resource within the region is minimal to negligible for most of the hydrological year.

5 Design rainfall depths

Based on the long daily record, various return periods were generated using the following statistical

methods and the best distribution fit, Log Pearson Type 3, was selected to determine the design rainfall

depths. The following table (Table 5-1) represents the calculated 24-hour rainfall depths from the

historical record between 1977 and 1999.

Table 5-1: Design rainfall depth for 24 hour period (SRK, 2018)

Design Storm (years) 1 in 2 1 in 5 1 in 10 1 in 20 1 in 50 1 in 100 1 in 200

Rainfall Depth (mm) 25 52 77 116 151 192 239

6 Stormwater Management Plan

The Department of Water and Sanitation (DWS) (previously known as the Department of Water Affairs

and Forestry (DWAF) and then the Department of Water Affairs (DWA)), has produced a range of Best

Practice Guidelines (BPGs) for the mining sector with each BPG having particular application to

different aspects of the mining process and to different components of the water management system

at a mine. BPG G1 (DWAF, 2006) provides four primary principles that need to be applied in the

development and implementation of a Storm Water Management Plan (SWMP). The first two

principles capture the clean and dirty water separation requirements of Regulation 704. The four

principles are as follows:

• Clean water must be kept clean and be routed to a natural watercourse by a system separate

from the dirty water system while preventing or minimising the risk of spillage of clean water

into dirty water systems. This will limit the reduction in water flow to the receiving water

environment/catchment (loss of water to the catchment) and thus increase the water available

in the water resource to other users.

• Dirty water must be collected and contained in a system separate from the clean water system

and the risk of spillage or seepage into clean water systems must be minimised. The

containment of dirty or polluted water will minimize the impact on the surrounding water

environment.



• The SWMP must be sustainable over the life cycle of the site and over different hydrological

cycles and must incorporate principles of risk management. Portions of the SWMP, such as

those associated with waste management facilities, may have to remain after site closure since

management is required until such time that the impact is considered negligible and the risk

no longer exists.

• The statutory requirements of various regulatory agencies and the interests of stakeholders

must be considered and incorporated.

Based on these principles and the guidelines in BPG G1, a framework for LDM’s SWMP was

developed.

6.1 Proposed Mine Infrastructure

A layout of the proposed mine infrastructure is shown in Figure 6-1 below. Based on the site catchment

delineation, the majority of the infrastructure will be located within catchments Cat_A and Cat_B

(Figure 6-2), following which these catchments will then be sub-divided to smaller Onsite

subcatchments around the major infrastructure areas such as the Opencast area, Pollution Control

Dam, Dumps, Offices and Workshops.

6.2 Regional catchment delineation

According to the published quaternary catchments of South Africa, the site infrastructure lies across

two quaternary catchments A72B and A72J. Based on this assumption, approximately 43% of the

Cygnus property lies in catchment A72B and the remainder (57%) lies in catchment A72J.

Based on the SRTM contour data catchment delineation, the catchment divide between A72B and

A72J bisects the property in the south eastern corner of the property. This means that, hydraulically,

approximately 91% (11.9 km2) of the Cygnus site drains towards the Brakrivier and therefore all

infrastructure for the proposed mine may impact only one quaternary catchment, catchment A72B.

Therefore only 9% of the site area, an area containing no proposed infrastructure, drain towards the

Sand River.

During the local catchment delineation, the site was found to lie within four (4) major catchments

namely Catchment A to D (denoted Cat A to Cat D). Two of the sub-catchments, Cat A and B, drain

northwards into the Brakrivier catchment (quaternary catchment A72B), while the remaining two drain

eastwards into the larger Sand River (Figure 6-2). The stream lines generated from Global Mapper

indicate the preferential pathway of runoff and in no way indicate the presence of actual streams on

the ground throughout the year. The following catchment characteristics in Table 6-1 were determined

for the local sub-catchments. These parameters represent the predevelopment scenario of the project

against which to compare the post-development scenario (the proposed coal mine and its

infrastructure).

Table 6-1: Catchment parameters for the local catchments

Catchment ID

Description Area (km2) Width (m) Flow Length (m) Slope (%)

Cat_A Regional 32.72 5,949 5,500 0.80

Cat_B Regional 5.20 1,528 3,400 1.00

Cat_C Regional 28.13 4,136 6,800 0.90

Cat_D Regional 22.55 3,580 6,300 1.10



Figure 6-1: Proposed site infrastructure



Figure 6-2: Cygnus local catchments in relation to quaternary catchments

Actual catchment divide

based on SRTM elevation

data



Generally, quaternary catchments are used for regional purposes and not site-specific purpose such

as stormwater management plans. Due to the location of both the Pollution Control Dam and Opencast

area falling hydraulically within A72B, the catchment delineation mentioned above and shown Figure

6-2 above was used to assess the impact of the proposed mine on the Mean Annual Runoff (MAR)

using WR2012 data for quaternary catchments.

6.3 Mean annual runoff

The 0.80 km2 opencast pit and the proposed 0.18 km2 Pollution Control Dam sub-catchment will both

reduce runoff generated within the immediate catchment. The catchment in which the pit is located is

32.7 km2. In addition, the CCM is situated in quaternary catchment A72B, which is 1554 km2 (see

Figure 3-2 above).

All site infrastructure where runoff will be contained on site will invariably cause a reduction in MAR.

based on this, only the Opencast Area and the PCD sub-catchment area (the Plant Area and Discard

Dump area) will lead to a reduction in MAR. The access roads will not have any significant increasing

effect on the MAR for both catchments A72B and A72J.

The effects of mining activity on the catchment MAR in which the pit and PCD are located, will be a

reduction in MAR. The results for the localised investigation are shown in Table 6-2. The captured

dirty water will result in a reduction of MAR of 45,900 m3.

Table 6-2: Natural MAR (from WR2012) and loss of MAR due to dirty water containment

Catchment Area

(km2)

A72B MAR contributing

rainfall (mm)

MAR from Catchment

(mill m3)

Dirty water area

(km2)

MAR from dirty water

(m3)

Loss of MAR

(%)

Opencast Pit 33 7 0.228 0.80 5 566 2.4

Pollution Control Dam

33 7 0.228 0.18 1 242 0.5

The effects of erecting buildings on the catchment MAR in which the all the buildings (workshop area,

contractor laydown area, parking area, etc.) are located, will be an increase in the MAR due to an

increase in impervious areas. The results for the localised investigation are shown in Table 6-2. The

diverted clean water will result in an increase of MAR of 2 259 m3.

Table 6-3: Natural MAR (from WR2012) and increase of MAR due to building constructions

Catchment Area (km2)

A72B MAR contributing rainfall (mm)

MAR from Catchment

(mill m3)

Dirty water area (km2)

MAR from dirty water (m3)

Loss of MAR (%)

Buildings 5.2 7 0.228 0.80 5 566 2.4

In the greater context, all the proposed infrastructure is located within quaternary catchment, A72B.

The net effect on the prevailing catchment MAR will be 0.04% reduction or 4 549 m3. The catchment

area and the associated MAR is presented in Table 6-4

The reduction in MAR included in Table 6-4 was estimated using the runoff depth given in WR2012

(Midgley, Pitman and Middleton, 1994).



Table 6-4: Quaternary natural MAR (from WR2012) and net loss of MAR due to dirty water containment

Catchment A72B Area (km2)

A72B MAR contributing rainfall (mm)

MAR from A72B

(mill m3)

Dirty water area (km2)

MAR from dirty water

(m3)

Loss of MAR A72B (%)

A72B 1554 7 10.83 0.98 6,808 0.04

6.4 Modelling

PCSWMM was used as a flood analysis model to determine peak discharges at each sub-catchment.

PCSWMM is a dynamic rainfall-runoff simulation model, based on the SCS-SA method, used for single

event or long-term simulation of runoff quantity. This model was set up for the site and used to calculate

the six-year recurrence interval flood peaks based on the design rainfall depths calculated in Section

5 above.

Manning’s ‘n’ coefficient used in the model for the impervious and pervious areas were 0.012 and

0.035 respectively. The Manning’s n for the pervious areas is based on medium to dense bush land

cover.

As inferred from the soils report by Scientific Aquatic Services (SAS, 2018), the soils were identified

as being predominantly of the sandy the loam group. The model uses this criterion to incorporate

infiltration into the analysis using the Green-Ampt infiltration method. This resulted in a Suction Head

of 110.1 mm, a Hydraulic Conductivity of 21.8 mm/hr and an Initial Deficit of 0.358 being used in the

modelling (Green and Ampt, 1911).

6.4.1 Stormwater catchment delineation

The based on the site infrastructure, the site was divided into both clean and dirty water sections

depending on the potential pollution sources and hence the likelihood of contact (dirty) and non-contact

water generation. These included:

• Dirty water areas: These are sub-catchment areas associated with the opencast pit area, the washing plant and the coal discard dump area. The area east of the opencast area consisting of the topsoil, hard and soft dumps has been deemed clean; and

• Clean water areas: The are sub-catchment areas associated with administration offices, parking lot, stores, contractor laydown areas and workshop areas. If any effluent is generated at these areas, such as the workshop area, it is isolated at source by means of localised sumps.

The sub-catchments for the various areas are shown in the table below.

Table 6-5: Clean and dirty water sub-catchments within the proposed mine

Sub-Catchment ID


S01 Clean 1.76 1171 1500 0.40

S02 Clean 0.13 427 300 0.50

S03 Clean 0.89 590 1500 0.40

S04 Clean 0.43 429 1000 0.10

S05 Clean 0.38 536 700 0.70

S06 Clean 0.19 338 550 0.01

S07 Clean 0.36 1184 300 0.50

S08 Clean 0.18 488 360 0.01

S09 Clean 0.11 190 600 0.70



Sub-Catchment ID


S10 Dirty 0.09 339 260 0.40

S11 Dirty 0.07 325 220 0.40

S12 Dirty 0.02 231 80 0.10

S13 Dirty 0.80 1354 590 0.10

6.4.2 Peak flows

The calculated results from the PCSWMM analysis presented in Table 6-6 shows the seven various

recurrence interval flood peaks for the upstream catchments draining the immediate study area. These

peak flows represent the pre-development scenario, the current state of the study area prior to mining

and addition of site infrastructure.

Table 6-6: PCSWMM method peak flows for each sub-catchment

Catchment Name


Peak Flow (m3/s)

2 year RI

5 year RI

10 year RI

20 year RI

50 year RI

100 year RI

200 year RI

S01 1.76 0.00 0.00 0.77 8.11 15.39 25.86 28.19

S02 0.13 0.00 0.00 0.23 1.78 3.16 5.03 5.42

S03 0.89 0.00 0.00 0.37 4.02 7.72 13.14 14.31

S04 0.43 0.00 0.00 0.26 2.54 4.69 7.76 8.42

S05 0.38 0.00 0.00 0.31 2.93 5.28 8.51 9.19

S06 0.19 0.00 0.00 0.20 1.78 3.13 4.93 5.30

S07 0.36 0.00 0.00 0.62 4.82 8.44 13.51 14.56

S08 0.18 0.00 0.00 0.27 2.22 3.78 6.13 6.62

S09 0.11 0.00 0.00 0.12 1.10 1.94 3.05 3.27

S10 0.09 0.00 0.00 0.27 5.13 9.92 16.79 18.33

S11 0.07 0.00 0.00 0.17 1.28 2.21 3.41 3.65

S12 0.02 0.00 0.00 0.33 5.58 10.86 18.52 20.16

S13 0.80 0.00 0.00 0.82 9.36 18.53 32.11 35.04

*RI: Recurrence Interval

For the post-development scenario, the sub-catchment areas were changed with altering the

catchment characteristics to reflect the proposed infrastructure. Peak flows were calculated for all

clean and dirty water sub-catchments. A comparison of the 1 in 50 and 1 in 100 year recurrence

interval peak flows for the pre-and post-development scenarios are shown below.

Table 6-7: Peak flows comparison between the pre- and post-development scenarios

Catchment Name


Peak Flow (m3/s)

50 Year RI 100 Year RI

Pre-development

Post-development

Pre-development

Post development

S01 1.76 15.43 30.27 25.93 44.78

S02 0.13 3.16 3.16 5.03 5.03

S03 0.89 7.72 10.73 13.14 16.37

S04 0.43 4.69 10.52 7.76 15.35

S05 0.38 5.28 13.57 8.51 19.31

S06 0.19 3.13 3.13 4.93 4.93



Catchment Name


Peak Flow (m3/s)

50 Year RI 100 Year RI

Pre-development

Post-development

Pre-development

Post development

S07 0.36 8.44 8.44 13.51 13.51

S08 0.18 3.78 3.78 6.13 6.13

S09 0.11 1.94 1.94 3.05 3.05

S10 0.09 9.92 3.19 16.79 4.66

S11 0.07 9.91 3.76 17.06 5.14

S12 0.02 9.88 1.18 17.08 1.53

S13 0.80 29.21 48.53 45.37 63.47

The proposed development and the subsequent management of clean and dirty water separation will

result in a peak flow increase in five (5) sub-catchment areas as a result of an increase in impervious

areas such as erection of buildings and a reduction (peak attenuation) in three (3) sub-catchment

areas due to storage and or flow diversion.

The highest peak flow increases occur in sub-catchments S05 (157%), S04 (124%) and S01 (96%).

These catchments may contain supercritical flows and any stormwater infrastructure will likely require

energy dissipation structures at their outlets such as gabions or rip rap. ,

6.4.3 Clean water management

The clean water management around site will consist of

The proposed Opencast Pit area and Plant Area are positioned mid-slope. The result is that it is a

requirement to manage potential ingress of clean water into the Opencast Pit and divert any clean

runoff away from the Plant and Discard Dump areas. Two main clean water diversion canals have

been proposed:

• Diversion Canal 1 will be positioned uphill of the Opencast Pit just downstream of the Topsoil,

Hards and Soft Dumps, which will allow water to be collected and routed away from the dirty area,

for release to the environment at two points around the Opencast Pit area; and

• Diversion Canal 2 will be positioned upstream of the Plant and Discard Dump Area, also allowing

for the water to be collected and routed away from the dirty area, for release to the environment

at two points around the area.

Five (5) culverts have been proposed to be constructed at various locations around the mine along

the haul and access roads to route water efficiently back into the environment.

The clean water area and associated channels and culverts are shown in Figure 6-3 and the sizes are

presented in Table 6-9 and Table 6-10 below.

6.4.4 Dirty water management

The dirty water at CCM is confined to the open cast pit and the plant and discard dump area. As per

common practice, the edges of the open cast will have a berm built up to prevent ingress of surface

water, in addition to the sized and designed clean water canal. The source of water to the open cast

section is therefore limited to direct rainfall and ground water seep.

Rehabilitation of the opencast pit will take place on the as the new pit blocks are opened following the

box-cut. This will gradually reduce the area available for direct rainfall to accumulate on the floor of

the pit. The rate of backfilling and rehabilitation is not known at this stage. Taking this into



consideration, for the purposes of the report, the total area of the pit was used in the calculation of

direct rainfall accumulation in the pit.

Removal of water from the open cast area requires a localised sump and installed pumping capacity

to deal with collected water. The nature of opencast mining requires a temporary sump to collect the

water and allow pumping. The position of the sump will move in relation to the mining operations until

the end of 2025. For the management of dirty water in the pit at Cygnus, it is proposed that the sump

be approximately 30 m by 30 m with a depth of approximately 3 m. The sump will provide a holding

capacity of 2,700 m3 which will be sufficient for the more common rainfall events.

The 1:50 and the 1:100-year rainfall events are more severe rainfall events and will require the bottom

bench to accumulate in water addition to the sump. The results for the volume of water captured and

temporarily stored prior to pumping are shown in Table 6 8. It is proposed that the dirty water from the

plant and discard dump areas be collected in a Pollution Control Dam situated just north of the Discard

Dump area (S12)

Table 6-8: Dirty water stormflow volume

Assumptions made in calculating the water contained in the pit, requiring pumping:

• Opencast will be completely open (0.80 km2).

The dirty water area and associated channels are shown in Figure 6-3 and the sizes are presented in

Table 6-9 and Table 6-10 below.

Catchment Name Area (km2) 1:50 (m3) 1:100 (m3)

Opencast Pit 0.80 53 268 73 519

Pollution Control Dam 0.18 16 082 18 789

Sump capacity (m3) 2 700 2 700



Table 6-9: Clean and dirty water channel arrangement and hydraulic properties for the 1 in 50 year design storm

Main Channel Name

Channel Section

Description Length

(m) Manning’s

n Cross Section

Depth (m)

Width (m)

Left slope (1:X)

Right slope (1:X)

Slope (m/m)

Max. Flow

(m³/s)

Max. Velocity

(m/s)

Max/Full Flow

(Fraction)

Max/Full Depth

(fraction)

Opencast Pit Diversion Canal

(Channel 1)

C1-01 Clean water channel 148 0.013 Trapezoidal 0.7 2.0 2.0 1.0 0.0020 1.58 1.38 0.35 0.74







Plant Diversion Canal (Channel 2)








Plant Dirty Water Canal (Channel 3)

C3-01 Dirty water channel 103 0.013 Trapezoidal 0.8 1.0 1.0 1.0 0.0059 0.00 0.00 0.00 0.00




Discard Dump Dirty Water

Canal (Channel 4)



Table 6-10: Culvert arrangement and hydraulic properties

Culvert Section Description Length

(m) Roughness Cross-Section

Depth (m)

Width (m)

Left slope (if appl.)

(1:X)

Right slope (if

appl.) (1:X)

Number of

Barrels

Culvert Code

Slope (m/m)

Max. Flow (m³/s)

Max. Velocity (m/s)

Max/Full Flow

Max/Full Depth

Inlet Control (fraction)

Culvert 1 Culvert Culverts 60 0.013 Closed Rectangular 1.0 1.0 0 0 1 53 0.0045 1.54 2.46 0.72 0.63 0.13

Outlet Culverts 67 0.013 Trapezoidal 0.5 1.0 3 3 1 0 0.0090 1.54 2.53 0.38 0.63 0





Culvert 4 Culvert Culverts 33 0.013 Closed Rectangular 1.6 1.0 0 0 4 53 0.0276 13.50 2.43 0.36 0.87 1


Culvert 5 Culvert Culverts 31 0.013 Closed Rectangular 1.4 1.0 0 0 4 53 0.0000 10.47 2.25 0.44 0.83 1




Figure 6-3: Proposed stormwater management plan for Cygnus Coal Mine



7 Water Balance

The water is undertaken as prescribed by the Best Practice Guideline G2: Water and Salt Balances

by DWAF, 2007.

Included in the study are the workshops, offices and the pit. Information was obtained where possible

from CCM. The average annual water balance is shown in Figure 7-1. The wet and dry scenarios are

presented in Appendix A (Figures A1 to A2).

7.1 Methodology

A high level annual, wet season and dry season water balance was set up based on a Microsoft Excel

spreadsheet. The water balance uses average monthly rainfall and evaporation for the hydrological

year. Average rainfall and other rainfall statistics for the various wet and dry rainfall scenarios have

been determined from observed long-term rainfall records.

Much of the water use indicated in the water balance is (currently) estimated by calculation because

the project is still in a development phase. These assumptions will need to be modified at a later stage

so that a dynamic water balance can be created and automatically updated. The key parameters used

in the water balance are shown in Table 7-1.

Table 7-1: Key parameters used for the water balance

Rainfall Evaporation Groundwater Potable water

Monthly rainfall

was used in the

water balance

Monthly evaporation

data was used in the

water balance

Groundwater figures were

obtained from the Mine Works

Programme report and a

Groundwater

inflows/discharge value of 0.1

l/s was used. This value will

be updated upon completion

of the groundwater study

0.20 m3 was

allocated per

person per day

and applied to a

staff complement

of 213 employees

and contractors.

Part of the role of the water balance is to present to the mine, the options available to decrease firstly

the cost to the mine of raw water supply through municipal infrastructure and secondly, to decrease

the reliance on the environment for water supply in new raw water use. The mine is able to save on

both of the above points by reusing water (dirty water) in their processes.

Groundwater collected in the sump of the opencast pit is classed as dirty water and as a result requires

containment, treatment and use, where possible. If the mine has an idea of the volume of water likely

to be classed as dirty, their reliance on the municipal raw water streams decreases by that amount.

This water balance will need to be incorporated into the overall mine water balance to determine if the

mine can accommodate extra mine water from the pump. Based on the balance, it is evident that mine

will need to implement water efficiency strategies as the bulk of losses will be due to evaporative

losses, with about 3.4% due to operational losses at this conceptual stage.



Figure 7-1: Annual average water balance for the proposed Cygnus Coal Mine

SRK Consulting: 477989 Page 23


8 Surface Water Impact Assessment

8.1 Impact Assessment Methodology

All specialists are required to assess each potential impact identified according to the following Impact

Assessment Methodology as described below.

This Impact Assessment Methodology has been formalised to comply the 2014 EIA Regulations of the

NEMA, which states the following:

An environmental impact assessment report must contain all information that is necessary for the competent authority to consider the application and to reach a decision, and must include –

• an assessment of each identified potentially significant impact, including –

(i) cumulative impacts;

(ii) the nature, significance and consequence of the impact and risk;

(iii) the extent and duration of the impact and risk;

(iv) the probability of the impact and risk occurring;

(v) the degree to which the impact and risk can be reversed;

(vi) the degree to which the impact and risk may cause irreplaceable loss of resources; and

(vii) the degree to which the impact and risk can be mitigated.

Specialists were required to identify impacts (positive and negative) associated with the project.

Specialists were also required to specify the type of impact (direct/indirect) and including an

assessment of cumulative impacts that may occur because of the proposed project. The anticipated

impacts associated with the proposed project were assessed according to SRK’s standardised impact

assessment methodology based on the following factors:

• Severity - the degree of change to the receptor status in terms of the reversibility of the impact; sensitivity of receptor to stressor; duration of impact (increasing or decreasing with time); controversy potential and precedent setting; threat to environmental and health standards;

• Spatial scope - the geographical scale of the impact;

• Duration - the length of time over which the stressor will cause a change in the resource or receptor;

• Frequency of activity - how often the proposed activity will take place; and

• Frequency of impact - the frequency with which a stressor (aspect) will impact on the receptor.

To enable a scientific approach for the determination of the environmental significance (importance)

of each identified potential impact, a numerical value has been linked to each factor. The interpretation

of the impact ratings are shown in Table 4-2 of the Impact Assessment Methodology prescribed.



8.2 Activities to be rated

Table 8-1 provides the anticipated activities relating to each project and project phase for which

potential impacts should be identified and assessed, and mitigation measures provided. Please note

that this table is not limited to only the stated activities identified, but should be used as a guideline

when determining and identifying activities that could have potential impact on the biophysical and

social environment.

Table 8-1: Cygnus Project Activities

8.3 Project activities with potential to impact surface water resources

Although it is recognised that existing legislation is in place that would not allow a project to be

developed that would have a material detrimental impact on surface water resources, there are a

number of potential impacts on water resources that can arise from mining activities related to both

Project Phase Activity

Pre-construction • Site clearing and grubbing of the footprint areas associated with the opencast pit

and box-cut, diversion canals, pipeline, buildings, and proposed access and haul roads.

Construction • Excavation of the pit, construction of diversion canals, pipeline, building (and foundations) and proposed access and haul roads.

Operation • Operation, management and maintenance of the opencast pit, workshop and contractors laydown areas, pipeline, and proposed access and haul roads.

• Operation, management and maintenance of the powerlines.

• Mining of the pit area.

Rehabilitation • The pit will be back-filled.

Post-closure • Demolition of all other project related infrastructure.

• Removal of all access and haul roads.

• Handling of potential contaminated soils.

• Monitoring of groundwater.



the volume and quality of water entering, or leaving, water resources which may include some of the

following:

• Reduced availability to downstream/down-gradient water users due to changes in water quantity or flow regime;

• Reduced availability of water to downstream water users due to changes in water quality;

• Reduced availability of water to surrounding water users due to physical obstruction from mine infrastructure pit and stormwater diversions etc.);

• Linear crossings of the watercourses may cause scouring around the infrastructure in the river;

• Damage to the aquatic ecosystem due to substances contained in releases from the mine;

• Scouring effect on stream banks and bed due to releases from the mine (clean water diversions, storm water drains, road culverts etc.);

• Increased erosion from areas of exposed soils; and

• Increased risk of flooding due to changes in catchment hydrology.

Impacts may be envisaged for the various phases of the pit development, being construction,

operational, closure and rehabilitation phases. The general activities that are common to construction

and rehabilitation of the pit, plant, discard dump and office building areas include the following:

• Removal of the vegetation.

• Removal and stockpiling of the topsoil.

• Earthworks and excavation of foundations for infrastructure e.g. buildings, roads, pipelines etc.

• Provision of stormwater management measures.

• Construction of concrete structures, pump stations and laying of pipelines.

• Rehabilitation of disturbed areas after general site construction is completed.

• Operation of the pit, on-going revegetation of berms around pit, water management systems, maintenance and monitoring.

• Decommissioning and closure of the pit once life of pit is reached.

• Rehabilitation of the pit and discard dump once decommissioning is completed.

• Post Closure including maintenance and monitoring.

8.4 Impacts associated with all activities

The impacts for all activities during the construction, operation and closure of the access roads,

opencast pit and diversion canals are discussed in greater detail below. They are detailed in Table 8-2

to Table 8-3.

8.4.1 Pre-construction - site clearing and grubbing of the footprint areas

An increase in erosion from cleared areas, topsoil stockpiles or any other area where there are

exposed soils can occur during storm events (direct impact). Increased erosion can result in an

increase in turbidity, suspended solids and sedimentation in the unnamed tributary (indirect and

cumulative impact). Some level of sedimentation is expected to occur in the Brakrivier pre-

development as runoff is naturally anticipated to pick up environmental debris as it crosses natural

areas.

Increased turbidity is reversible and surface water should return to pre-impact turbidity levels once

sediment levels entering the watercourse are reduced. Settled sediments should naturally move

downstream during periods of high flow flowing storm events.

By minimising the area cleared for construction the potential for erosion will be reduced. Construction

of appropriate stormwater controls in the form of clean water diversion bunds upstream of the

construction site and paddocks downstream of the working activities will minimise the sediment loads



leaving the construction area. Such sediments will be further reduced by temporary erosion

prevention berms or similar measures within the path of the diverted clean water.

Rehabilitation of disturbed areas immediately after construction will facilitate re-establishment of

vegetation thus reducing the potential for erosion post-construction.

8.4.2 Impacts during closure/rehabilitation

Similar water quality and erosions impacts as in the construction phase have the potential to occur

during the demolition of infrastructure and rehabilitation of the pit and associated infrastructure despite

the pit becoming a permanent fixture in the landscape. No additional impacts are envisaged as this

activity should be restricted to the already disturbed area. These impacts will therefore be addressed

in the construction phase.

The pit will be revegetated to manage on-going dust generation and erosion after back-filling. All

rehabilitation activities should be monitored until vegetation is well established and no further surface

water quality impacts are deemed likely.

8.4.3 Post-closure

The main activity identified during the post-closure phase that has the potential to impact on surface

water resources is dispersion of the contaminated groundwater plume which is discussed in the

groundwater specialist report.

During the post-closure phase, all infrastructures will have been removed; therefore the surface water

quality should not be further impacted by any of the post-closure activities.

8.5 Impacts associated with the pit, plant area and associated infrastructure (e.g. pipelines, stormwater management)

8.5.1 Construction of the pit and associated infrastructure (access roads, pipelines)

Changes to surface water hydrology could result due to placement of infrastructure within drainage

lines and containment of dirty runoff within the pit footprint Without adequate clean water diversions

or suitable grading of areas there is an increased risk of flooding upstream (impedance of flow) which

could result in damage to property and infrastructure. The impact will be localised but will remain

throughout the life of the mine. The probability that local water courses will be diverted and will not

carry the water falling directly on the pit and considered dirty water, is definite and the overall

significance of the impact is rated as medium high. The impact will affect the flow regime and

morphology of the watercourse and thus overall functionality of the local surface water courses. Water

course functions are beyond the scope of this study and are described in the biodiversity or similar

study.

Appropriately designed and constructed clean water diversion structures and outlets in compliance

with Regulation 704 will return clean water runoff generated up gradient of the pit to the Brakrivier in

a manner as close to natural/pre-mining conditions as possible. Energy dissipaters should be

constructed at points where there are concentrated discharges of water to the environment that could

cause significant erosion and scouring within water channels to reduce the energy and speed of the

water flow. This is applicable to the Clean Water Diversion Canal 2 and the two dirty water channels

at the discard dump and plant area.

Appropriately designed and constructed structures and stormwater outlets in compliance with

Regulation 704 will reduce the potential for erosion. Erosion protection and energy dissipaters should



be constructed at points where there are concentrated, high velocity flows of water to the environment

that could cause significant erosion to slow the speed of water. The standard WUL conditions require

that construction takes place in the dry season and starts from upstream to downstream with

concurrent rehabilitation taking place. Weekly water monitoring is also required during construction

and for three months post construction.

8.5.2 Operation of the Opencast Pit and Plant Area

Changes to the hydrology within the Brakrivier catchment will continue from the construction phase

and no additional mitigation is indicated.

The rainfall water within the designated dirty water areas of the Opencast Pit and Plant and Discard

Dump Area that form part of the MAR to the local water courses will continue to be removed from the

catchment and may continue to reduce the quantity of water available to downstream users.

The potential for contamination of surface water due to releases of dirty water (runoff and return water)

from all access roads due to transportation of product remains of moderate significance both pre- and

post-mitigation. It is recommended that regular dust suppression be conducted as far as possible using

water from the pollution control dam thereby keeping the PCD as close to empty as possible to allow

for accommodation of the design storm.

Spillages and accidental discharges could result in the contamination of surface water resources.

Spillage of return water from the piped transfer systems has the potential to impact indirectly on the

Brakrivier via cumulative waste load build-up and subsequent wash off during storm events (via runoff).

The impact is of medium high significance but can be mitigated by maintaining the PCD as close to

empty as possible and reversible through a combination of clean-up and assimilation/natural recovery

in the watercourse.

8.5.3 Operation of the buildings and workshop areas

Changes to the hydrology within the Brakrivier catchment will continue from the construction phase

and no additional mitigation is indicated. The rainfall and storm water within the buildings and

workshop areas will result in increased peak flows due to the impervious nature of the ground being

introduced. The effluent generated within workshop the workshop areas should be controlled and

managed using localised sumps at various areas.

The potential for contamination of surface water due to releases of dirty water (runoff and return water)

remains of medium high significance for the pre-mitigation scenario due to high concentration as a

result of pollutant build up, and can be improved to a low rating for the post-mitigation.

Spillages and accidental discharges could result in the contamination of surface water resources.

Spillage from these areas also have the potential to impact indirectly on the Brakrivier via cumulative

waste load build-up and subsequent wash off during storm events (via runoff) but the impacts will be

very localised to the areas due to proximity limitations of the first flush event. The impact is of moderate

significance but can be mitigated and reversible through a combination of on-site clean-up using spill

kits and assimilation/natural recovery in the watercourse or drainage areas.



Table 8-2: Impact assessment for the access roads

Type of Impact POTENTIAL IMPACT DESCRIPTION IN

TERMS OF ENVIRONMENTAL ASPECTS

ENVIRONMENTAL SIGNIFICANCE BEFORE MITIGATION



IMPACT MANAGEMENT OUTCOME (ENVIRONMENTAL SIGNIFICANCE AFTER MITIGATION)


(%)

Consequence Likelihood

(Probability) Significance (Degree to

which impact may

cause irreplaceable

loss of resources)

Significance Rating



which impact may

cause irreplaceable

loss of resources)

Significance Rating

Seve

rity

Spat

ial

Du

rati

on

Fre

qu

ency

: A

ctiv

ity

Fre

qu

ency

: Im

pac

t

Seve

rity

Spat

ial

Du

rati

on

Fre

qu

ency

: Act

ivit

y

Fre

qu

ency

: Im

pac

t


Direct Increased solids transport due to clearing/grubbing

4 1 1 2 3 30 Medium

Low Construct in dry season and install silt bunds

2 1 1 2 3 20 Low 33

Indirect Increased runoff requiring retention on site

4 1 1 1 3 24 Low Limit footprint and install retardation structures

2 1 1 1 3 16 Low 33


5 1 1 2 4 42 Medium

High Operate using best practices 2 1 1 2 4 24 Low 43

Construction Phase

Direct Impeding flow while under construction 4 1 1 3 2 30 Medium

Low

Construct in dry season.

3 1 1 2 2 20 Low 33 Protect with gabions & mattresses.

Remove litter & debris to stop blocking.

Direct Accidental spillages of hazardous substances from construction vehicles used during construction of the crossings.

5 1 2 4 4 64 Medium

High


2 1 2 2 4 30 Medium

Low 53



Clean spillages immediately they occur and remediate as necessary using spill kits.


4 1 2 3 2 35 Medium

Low


2 1 2 3 2 25 Low 29




Direct Debris from poor handling of materials and/or waste blocking watercourse

2 1 2 4 2 30 Medium

Low Operate using best practices 2 1 2 3 2 25 Low 17

Operational Phase

Direct Debris from upstream blocking watercourse at pipes/canals/culverts

1 2 4 4 3 49 Medium

High Operate using best practices 1 2 2 4 2 30

Medium Low

39




Type of Impact POTENTIAL IMPACT DESCRIPTION IN

TERMS OF ENVIRONMENTAL ASPECTS






(%)



which impact may

cause irreplaceable

loss of resources)

Significance Rating



which impact may

cause irreplaceable

loss of resources)

Significance Rating

Seve

rity

Spat

ial

Du

rati

on

Fre

qu

ency

: A

ctiv

ity

Fre

qu

ency

: Im

pac

t

Seve

rity

Spat

ial

Du

rati

on

Fre

qu

ency

: Act

ivit

y

Fre

qu

ency

: Im

pac

t

Direct Debris blocking watercourses if road continues to be used by the community.

1 2 4 4 3 49 Medium

High

Community needs to remove litter & debris to prevent blocking.

1 2 2 2 3 25 Low 49

Direct Impeding flow while under demolition 3 2 2 1 3 28 Medium

Low Demolish infrastructure as far as possible in the dry season

1 2 2 1 3 20 Low 29

Direct Increased turbidity due to demolition. 3 2 1 2 4 36 Medium

Low Demolish during dry season, limit the disturbed footprint.

1 2 2 1 3 20 Low 44

Direct Accidental spillages of hazardous substances from construction vehicles used during demolition.

3 2 1 2 4 36 Medium

Low

Operate using best practices and clean spillages immediately they occur and remediate as necessary using spill kits.

1 2 1 2 4 24 Low 33

Post-Closure Phase

Direct Flooding caused by extreme rainfall event 4 2 1 1 4 35 Medium

Low

Warning signs to discourage crossing if pipes/culverts are submerged.

2 2 1 1 4 25 Low 29

Direct Damage to the crossings themselves 4 2 1 1 4 35 Medium

Low

Regular periodic inspections by successor in title and remediation as necessary.

2 2 1 1 3 20 Low 43



Table 8-3: Impact assessment for the opencast pit and plant area

Type of Impact



IMPACT MANAGEMENT ACTIONS (PROPOSED MITIGATION MEASURES)



(%)



which impact may

cause irreplaceable

loss of resources)

Significance Rating



which impact may

cause irreplaceable

loss of resources)

Significance Rating

Seve

rity

Spat

ial

Du

rati

on

Fre

qu

ency

: Act

ivit

y

Fre

qu

ency

: Im

pac

t

Seve

rity

Spat

ial

Du

rati

on

Fre

qu

ency

: Act

ivit

y

Fre

qu

ency

: Im

pac

t


Direct Water runoff requiring retention on site 3 1 1 1 2 15 Low Construct in dry season;

1 1 1 1 2 9 Low 40 Limit footprint.


4 1 1 4 2 36 Medium

Low Operate using best practices 4 1 1 2 2 24 Low 33

Construction Phase

Direct Impeding flow while under construction 4 1 2 1 3 28 Medium

Low

Construct in dry season and

2 1 2 1 3 20 Low 29 protect with gabions & mattresses and

remove litter & debris to stop blocking.

Direct Accidental spillages of hazardous substances from construction vehicles used during construction of the crossings.

4 1 2 2 3 35 Medium

Low


2 1 2 2 3 25 Low 29



Clean spillages immediately they occur and remediate as necessary.


4 1 2 2 3 35 Medium

Low


3 1 2 2 2 24 Low 31




Indirect Separate clean and dirty water streams 3 3 3 1 2 27 Medium

Low Construct diversion drains timeously 2 2 3 1 2 21 Low 22

Operational Phase

Indirect Pump failure will result in dirty water accumulation in the pit

4 1 1 1 4 30 Medium

Low

Undertake regular structural inspections of pumps and pipes exiting pit. Ensure groundwater investigation is done to understand groundwater levels.

2 1 1 1 4 20 Low 33

Direct Reduction in catchment Mean Annual Runoff

2 3 4 4 2 54 Medium

High

Minimise dirty water areas requiring containment as far as practically possible

2 1 2 3 2 25 Low 54

Direct Spilling of the pollution control dam 2 3 4 4 2 54 Medium

High

Maintain stormwater levels as close to empty as possible by using it for dust suppression

2 3 2 1 2 21 Low 61



Type of Impact



IMPACT MANAGEMENT ACTIONS (PROPOSED MITIGATION MEASURES)



(%)



which impact may

cause irreplaceable

loss of resources)

Significance Rating



which impact may

cause irreplaceable

loss of resources)

Significance Rating

Seve

rity

Spat

ial

Du

rati

on

Fre

qu

ency

: Act

ivit

y

Fre

qu

ency

: Im

pac

t

Seve

rity

Spat

ial

Du

rati

on

Fre

qu

ency

: Act

ivit

y

Fre

qu

ency

: Im

pac

t

Indirect High rate of ground water ingress 4 3 4 1 2 33 Medium

Low

Implement recommendations from groundwater study with regards to pumping and dewatering

2 3 3 1 2 24 Low 27


Direct Pit reaching capacity and overflowing to the environment.

3 1 4 1 4 40 Medium

High Understand groundwater in the area and optimise mine planning activities

2 1 3 1 3 24 Low 40

Post-Closure Phase

Indirect Water quality changes downstream 3 1 4 1 4 40 Medium

High

Maintain stormwater collection system and monitoring. Consider an treatment effluent treatment plant if decanting is envisaged from the groundwater study

2 1 2 1 2 15 Low 63



9 Conclusions and Recommendations

The surface water specialist study provides an indication of the steps and processes required in order

to meet the Regulation 704 criteria. These include the;

• Separation of clean and dirty water streams and the release and containment of each stream respectively by constructing diversion berms and canals;

• Assessment of the impact of MAR changes on the local and quaternary catchment level

• Operating water balance for the mine, especially the Opencast Pit

• Groundwater collected in the sump of the opencast pit requires containment, treatment and or use, where possible;

• Constructing five culverts at various locations around the mine along the haul and access roads to route water efficiently back into the environment

The opencast pit requires a clean water cut off canal to the south west to prevent the situation of

surface runoff from entering the opencast pit during rainfall events. The canal will discharge the water

to the west and east as it straddles a high point in the middle of the canal.

The nature of a pit excavation results in a reduced likelihood of dirty water, generated at the opencast

pit, flowing into the environment. A sump has been proposed for the pit as a means of creating a point

from which to pump the water out and to a suitable containment and treatment location.

The rainfall and storm water within the buildings and workshop areas will result in increased peak flows

of the local catchment but any effluent generated within workshop areas should be controlled and

managed using localised sumps at various isolated areas.

The effects of mining activity on the catchment MAR in which all infrastructure are located, will be a

reduction a reduction of MAR of 43 641 m3 per annum (0.5%) on a local scale and 0.04% on a

quaternary catchment scale. With the mining activity located about 3 km away, this further lowers the

likelihood of negative impacts on the nearest surface water resource, the Brakrivier.

The project area is located in a very dry region of the Water Management Area resulting in a reduced

to absence of surface runoff for the majority of the year. As a result, the mine is likely to experience a

deficit in surface water supply resulting in an exclusive use of groundwater for the operations. The

foregoing ultimately results in surface water quality changes in the environment being very low.



Prepared by

Oliver Malete, Pr. Sci. Nat.

Hydrologist

Reviewed by

Peter Shepherd, Pr. Sci. Nat.

Partner

All data used as source material plus the text, tables, figures, and attachments of this document have

been reviewed and prepared in accordance with generally accepted professional engineering and

environmental practices.



10 References

Department of Water Affairs and Forestry (2000) Regulation 704: Operational Guideline No. M6.1.

Guideline document for the implementation of regulations on use of water for mining and related

activities aimed at the protection of water resources. Second Edition. Pretoria, South Africa.

Department of Water Affairs and Forestry (2006), Best Practice Guideline G1: Storm Water

Management, Pretoria, South Africa.

Smithers, J and Schulze, R (2002) Design rainfall and flood estimation in South Africa. Water Research

Commission Report No. K5/1060. Pretoria, South Africa



Appendices



Appendix A: Wet and Dry Seasons Water Balance



Figure A-1: Wet season scenario water balance



Figure A-2: Dry scenario water balance



SRK Report Distribution Record

Report No. 535300

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Name/Title Company Copy Date Authorised by

Ndomupei Masawi SRK Consulting, Pretoria 1.pdf 2019/08/03 P Shepherd

Library SRK Consulting HC 2019/08/03 P Shepherd

Approval Signature:

This report is protected by copyright vested in SRK (SA) (Pty) Ltd. It may not be reproduced or

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Documents

Cygnus Coal Mine Surface Water Specialist Study · • Separation of clean and dirty water streams and the release and containment of each stream respectively by constructing diversion