Appendix 19 - gcs-sa.biz · Appendix 19 WATER BALANCE. 63 Wessel Road, Rivonia, 2128 PO Box 2597,...

Appendix 19

WATER BALANCE

63 Wessel Road, Rivonia, 2128 PO Box 2597, Rivonia, 2128 South Africa

Tel: +27 (0) 11 803 5726 Fax: +27 (0) 11 803 5745 Web: www.gcs-sa.biz

GCS (Pty) Ltd. Reg No: 2004/000765/07 Est. 1987

Offices: Durban Johannesburg Lusaka Ostrava Pretoria Windhoek

Directors: AC Johnstone (Managing) PF Labuschagne AWC Marais S Pilane (HR) W Sherriff (Financial)

Non-Executive Director: B Wilson-Jones

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Somkhele Mine, KwaZulu-Natal: Water Balance

Report

Version – 1

04 March 2018

Tendele Coal Mining (Pty) Ltd.

GCS Project Number: 16-1243

Client Reference: GCS Somkhele Water Balance

Tendele Coal Mining (Pty) Ltd. Somkhele Mine: Water Balance

16-1243 Macrh 2018 Page II

Report Version – 1

03 May 2017

Tendele Coal Mining (Pty) Ltd.

16-1243

DOCUMENT ISSUE STATUS

Report Issue Final

GCS Reference Number GCS Ref - 16-1243

Client Reference GCS Somkhele WSB Study

Title Somkhele Mine, KwaZulu-Natal: Water Balance Report

Name Signature Date

Author Haden Jacobs 3 March 2018

Document Reviewer Kevin Bursey

4 March 2018

Director Pieter Labuschagne

8 March 2018

LEGAL NOTICE This report or any proportion thereof and any associated documentation remain the property of GCS until the mandator effects payment of all fees and disbursements due to GCS in terms of the GCS Conditions of Contract and Project Acceptance Form. Notwithstanding the aforesaid, any reproduction, duplication, copying, adaptation, editing, change, disclosure, publication, distribution, incorporation, modification, lending, transfer, sending, delivering, serving or broadcasting must be authorised in writing by GCS.


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EXECUTIVE SUMMARY

GCS Water and Environment (Pty) Ltd. (GCS) was appointed by Tendele Coal (Pty) Ltd. to

undertake a static Excel platform water balance for the Entire mine operation, including

offices, Pits and dust suppression at the Somkhele Anthracite Mine in the KwaZulu-Natal

Province of South Africa (see Figure 1.1).

The water balance model is based on data provided by the mine and was calibrated using

recorded data for several components of the mine. It is recommended that the model is re-

run using longer calibration records and updated values, when these become available.

The monitoring network of flow meters should be upgraded and extended to increase the

knowledge of the mine water system. It is recommended that focus also be placed on:

• The water levels in the various dams and opencast pits; and

• The transfer of water between Pollution Control Dams (PCDs), Water Supply Dams

(Myenge 1 and 2, River Dam and Settling ponds 1, 2, 3 and 4) and the Plant Header

Dam.


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GLOSSARY OF TERMINOLOGY

Open Pit Mining: Open pit mining, or open-cast mining is a surface mining technique of

extracting rock or minerals from the earth (close to the surface) by their removal from an

open pit. The excavated surface is called the open pit.

Discard Dump: Coal mining and processing produces low grade coal and rock waste referred

to as discards. The discards are stored in a discard dump facility.

Pollution Control Dam: Pollution control dams (PCDs) form an integral and important part of

the water management systems on a mine. The purpose of PCDs for the mine and in the water

management circuits are to minimise the impact of polluted water on the water resource,

minimise the area that is polluted as far as possible, by separating out clean and

dirty catchments, and to capture and retain the dirty water contribution to the PCDs that

cannot be discharged to the water resource, due to water quality constraints, and manage

this dirty water through recycling, reuse, evaporation and/or treatment and authorised

discharge.

Operational Philosophy: The operational philosophies describe the processes employed by

the mine in terms of water. The operational philosophy would include pumping capacities,

the conditions of pumping, plant water demands etc. The operational philosophy describes

the practical conditions employed by the mine when moving water through the system.

Infiltration: Infiltration is the process by which water on the ground surface enters the soil.

Evaporation: Evaporation is the process by which water is converted from its liquid form to

its vapour form and consequently transferred from land and water masses to the atmosphere.

Percolation: Percolation refers to the movement fluids through porous materials. In this case

it refers to the ability of soil to absorb water.

Return Water Dam (RWD): A storage dam used to pump water from a pit.

Tailing Storage Facility (TSF): A dam or pit where tailings from the plant are stored.


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CONTENTS PAGE

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

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

3 METHODOLOGY ......................................................................................................................... 4

4 WATER SCHEMATIC .................................................................................................................... 6

5 MODELLING DESCRIPTION .......................................................................................................... 8

5.1 WATER BALANCE MODEL ................................................................................................................ 8 5.2 GENERAL MODEL DESCRIPTION ........................................................................................................ 8 5.3 ELEMENT MODELLING .................................................................................................................... 9

5.3.1 Dam Element .................................................................................................................... 9 5.3.2 Plant Element .................................................................................................................... 9 5.3.3 Climate ............................................................................................................................ 10 5.3.4 Evaporation..................................................................................................................... 11

5.4 AVAILABLE DATA ......................................................................................................................... 12 5.4.1 Dam Capacities and Areas .............................................................................................. 12 5.4.2 Pumping Capacities ........................................................................................................ 13

5.5 RESULTS .................................................................................................................................... 13

6 CONCLUSIONS .......................................................................................................................... 17

7 RECOMMENDATIONS ............................................................................................................... 17

8 REFERENCES ............................................................................................................................. 18

LIST OF FIGURES

Figure 2.1 Somkhele Mine Extent and Locality .................................................... 3 Figure 2.2. Somkhele Water Balance Labels ........................................................ 4 Figure 4.1 Somkhele Colliery site-wide water balance schematic ............................. 7 Figure 5.1 Mean monthly S-Pan evaporation values for the study area. ..................... 12 Figure 5.2 Simulated average annual mine water balance ..................................... 14 Figure 5.3 Simulated wet season mine water balance .......................................... 15 Figure 5.4 Simulated dry season mine water balance ........................................... 16

LIST OF TABLES

Table 2.1 Somkhele Water Reticulation Names ................................................... 4 Table 5.1 Details for rainfall station 0339352W (Kangela). .................................... 10 Table 5.2 Dam capacities used in the modelling ................................................ 12


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1 INTRODUCTION

GCS Water and Environment (Pty) Ltd. (GCS) was appointed by Tendele Coal (Pty) Ltd. to

undertake a static water balance for the opencast mining activities at the Somkhele

Anthracite Mine in the KwaZulu-Natal Province of South Africa.

Somkhele Mine is situated in Quaternary Catchments W23A and W32G and Water Management

Area (WMA) 6 (Usutu to Mhlatuze), the mine obtains its water from the Mfolozi River (see

Figure 2.1) with direct pumping from the river as well as a bank of boreholes in the river bank

when flow is too low to directly pump from the river.

Accurate water and salt balances are considered to be one of the most important and

fundamental water management tools available to the mines. The purpose of water and salt

balances includes:

• Providing the necessary information that will assist in defining and driving water

managementstrategies.

• Auditing and assessment of the water reticulation system, with the main focus on water

usage and pollution sources. This includes identifying and quantifying points of high water

consumption or wastage, as well as pollution sources. Seepage and leakage points can also

be identified and quantified when the balances are used as an auditing and assessment

tool.

• Assisting with the design of storage requirements and minimising the risk of spillage.

• Assisting with the water management decision-making process by simulating and evaluating

various water management strategies before implementation.

2 SCOPE OF WORK

The scope of work undertaken is outlined as follows:

• Hydrology Update:

o A climate and rainfall evaluation was undertaken;

• Water Balance:

o An Excel-based water process flow diagram was generated. The water

balance model was based on the client-approved process flow diagram; and


16-1243 4 May 2017 Page 2

o An Excel-based water balance was developed. This water balance was based

on the operational philosophy as described by Somkhele personnel.

• Reporting:

o A project close-out report detailing the assumptions made and the results of

all of the activities listed above was written; and

o Recommendations were made for additional work and data requirements, if

needed.


16-1243 04 March 2018 Page 3

Figure 2.1 Somkhele Mine Extent and Locality


16-1243 4 May 2017 Page 4


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3 METHODOLOGY

The study commenced with a desktop assessment of the area of interest and included

identification of existing data and literature pertaining to the area.

Climate data were obtained from the South African Weather Service (SAWS) and/or databases

of WR2012.

As mentioned, Excel software was used for the Water Balance calculations. The model was

based on the mine’s operational philosophy, as explained by mine personnel.

Relevant software employed throughout the study included:

• ArcView10.1 for Geographic Information Systems (GIS) work and mapping;

• Excel software for creating Process Flow Diagrams;

• Excel Software for Water Balance Modelling, and

This study was undertaken with adherence to the relevant South African Best Practice

Guidelines and Acts. The Water Balance update will be undertaken according to the

Department of Water and Sanitation; DWS (previously Department of Water Affairs; DWA)

Guidelines; Best Practice Guidelines (BPG) G2: Water and Salt Balances.


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4 WATER BALANCE

The mine-wide water balance at Somkhele Mine consists of multiple opencast pits, Plants

(Plants 1, 2 and 3), a Discard Dump, a called Pit A, North Pit Return Water Dam (RWD), Pit A

RWD, a number of water supply dams (River Dam, Mfolozi New Dam, Myenge Dam 1 and 2,

Settling ponds 1, 2, 3 and 4 and Plant Header Dam). There are three PCDs located on the site

(Plant PCD, Workshop PCD and Platform PCD). Figure 4.1 shows a schematic of the water

circuits on the mine which are modelled in the water balance and Figure 2.1 shows the mine

layout.

The mine water circuit consists of the following facilities:

• Pit areas: The Pit Areas (North Pit, Pit B, D, E and Pit A) generates water by means

of direct rainfall into the pit, runoff and groundwater inflow. Water that accumulates

in the pit is dewatered to the North Pit RWD, and Pit A RWD, however water

generated from Pit B, D, E is used for Dust Suppression of Area 2 directly. Pit A RWD

is used to feed water to the Plant Header Dam, via Recycle Ponds 1,2,3,4;

• Water abstracted from the Umfolozi River is pumped into the unlined River Dam New

then to the unlined Myenge Dam 2 and fed directly to the Plant when needed. The

Plant Header Dam is the primary source of water for the Plant as it is filled with

recycled water. Myenge Dam 1 receives water from the Platform PCD as well as

overflow from the Recycle Ponds. The Recycle Ponds receive water from Pit A. The

Plants 1, 2 and 3 sources its water from the Plant Header Dam directly which is

supplemented with clean water from Myenge Dam 2 when required;

• Slurry from the Plants is pumped to Pit A (TSF) which returns water to the Pit A RWDs

1 and 2;

• Surface water runoff generated from the Plant Area, Product Stockpiles and

Workshop Area are collected in the Plant and Workshop PCDs. This water is then

pumped from Myenge Dam 1 to the Settling ponds. The Settling ponds also receive

surface water runoff from the Discard Dump areas. The water contained in the

Settling ponds is used to supply the Plant Header Dam.

• The Plant Header Dam supplies the Plants with water to meet the Plant Demand. This

relationship was identified as the main driver of the system.


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Figure 4.1 Somkhele Colliery site-wide water balance schematic

Umfolozi and Borehole

abstraction

Seepage

Rainfall

Myenge 2

m3

Myenge 1

River Dam Evaporation

Mfolozi Old Dam

Pit BDE

Settling Dam1,2,3,4

Plantstorm

water dam

Plant 1,2,3

Workshop PCD

Generator dam

North and South Pit

North Pit RWD

Dust

Suppression

DiscardDump

Stock Pi le

Pit A

Pit A RWD

Platform PCD

Rainfall

Rainfall

Rainfall

Rainfall

Rainfall

Evaporation

Evaporation

Evaporation

Rainfall

Seepage

Seepage

GW Ingress

GW Ingress

Evaporation Evaporation

Rainfall

Runoff

Evaporation

Rainfall

Rainfall

Rainfall

Rainfall

Evaporation

Rainfall

Evaporation

Evaporation

Evaporation

Evaporation

Rainfall

Evaporation

Evaporation

Rainfall

Rainfall

Evaporation

Evaporation

Dust Suppression

Kwaluhlanga RWD

Dust

Suppression

GW Ingress

Runoff

Evaporation


16-1243 4 May 2017 Page 8

5 MODELLING DESCRIPTION

5.1 Water Balance Model

Typically, mine water balances are focused around the tailings area, plant processes and pit

areas. The classic water balance approach usually involves building a deterministic model in

which respective elements of the water cycle are usually represented using averaged values

of system variables over modelled time steps. Many of these variables are well known in

advance, and can be accurately defined. However, hydrological processes and plant processes

are often probabilistic by nature (there is uncertainty in the processes), and using their

average values (such as a fixed runoff percentage as a runoff estimate) limits the accuracy

and usefulness of the model outputs. Furthermore, a deterministic model does not usually

account for extreme meteorological events, which may have direct implications for water

supply and disposal, and quite often determine important design requirements during the

design and approval processes.

5.2 General Model Description

The mine uses a system of dams, pumping systems, diversions and management options such

as dust suppression and evaporation to manage the water on the mine complex. To represent

the mine water management system, the following elements have been included in the

model:

• Dams;

• Tailings Storage Facility;

• Plants;

• Pits, Workshops and Discard Dumps

• Climatic elements.

The above elements can be used to build up a mine water system. The operating rules and

connectivity govern how the water streams produced from the various elements are linked

together.

• The time step of the model is dependent on the objective of the model.


16-1243 4 May 2017 Page 9

• An annual time step can be used to give an indication of the average water volumes

that may need to be managed and an overall indication of the mine water balance.

Such a large time step does not, however, address the seasonal or daily variations

and therefore cannot be used to size storage facilities.

• A monthly time step accounts for the seasonal variations and can be used to provide

indicative sizing of storage facilities such as PCDs. The monthly time step can also be

used to provide an indication of the capacities of the pumping pipeline infrastructure

needed to convey the water between storage elements.

• A daily time-step accounts for daily weather changes and is used to sized PCD`s as

well as storm water management.

5.3 Element Modelling

5.3.1 Dam Element

The dam element is a storage element, with inflows and outflows.

The inflows to the Dam element are:

• Pumping inputs which could be one of the routes from the mine workings or pumping

from other dams in the system or groundwater inflows.

• Rain, which is the rainfall falling directly on the surface of the dam. This is calculated

as the daily rainfall depth multiplied by the water surface area of the dam.

The outputs from a typical dam are:

• Evaporation from the surface of the dam, which is calculated as the product of the

evaporation depth for water body times the water surface area.

• Seepage from the dam floor, which is calculated as the product of a seepage rate

and the water surface area in the dam. The seepage is assumed to leave the mine

water system.

• Pumping from the dam

• Spillage, which from the dam occurs when the dam is full and overflows.

5.3.2 Plant Element

The water circuits within the plant are not included in the water balance model. This is

known as a black box approach, where the inflow and outflow water values are measured

and the difference is assumed to be lost as process water. The water requirements of the

plant are dependent on the ore processed in the plant.


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Inputs to the plant are:

• The water into the plant required to run the plant. The water volume is calculated

by undertaking a water balance across the plant.

• The recycle from the TSF. This is estimated as a fraction of the water that goes out

with the slurry. Recycle water is also received from the Settling Ponds 1,2,3,4. Water

to top up the system is received directly from Myenge Dam 2.

The outputs from the plant:

• The water in the slurry pumped to the TSF. The water in the slurry is calculated using

the slurry density, the mass of solids in the slurry and the specific gravity of the ore.

• Water from the Stockpile and Discard dump which go to the Plant Header Dam.

• Losses are the losses incurred within the plant. These losses are the moisture in the

product, the moisture in the slurry and the moisture in the discard.

5.3.3 Climate

5.3.3.1 Rainfall

The daily rainfall record for the rainfall station 0339352_W (Kangela) (see Table 5.1 for

details) was sourced and used in this study. The locality of the Kangela rainfall station in

relation to the site is shown in Figure 2.1. The monthly rainfall distribution illustrated in

Figure 5.1.

Table 5.1 Details for rainfall station 0339352W (Kangela).

Name of the

rainfall station

Rainfall

station

number

Distance

(km)

Latitude

(°)(‘)

Longitude

(°)(‘)

Record (Years) MAP (mm)

Kangela 0339352_W 18.1km 28°12‘ 32°12‘ 129 761


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Figure 5.1 Monthly Rainfall distribution. 5.3.4 Evaporation

The mean annual Symons-pan (S-Pan) evaporation in the project area was found to be

1399mm (WR2012). The evaporation zone for the W23A and W32G quaternary were found to

be 22C. Average monthly evaporation values are presented in Figure 5..

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

10th Percentile 30.5 37.7 32.0 29.2 33.6 29.0 17.5 5.8 4.1 4.1 4.0 10.9

30th Percentile 48.1 65.6 59.7 66.7 58.8 58.2 27.7 11.7 10.6 10.8 12.3 23.0

50th Percentile 77.9 86.0 76.9 93.9 93.6 82.2 50.5 19.5 20.8 18.7 19.6 39.0

70th Percentile 102.8 111.5 112.3 129.9 139.3 119.0 74.0 41.9 47.9 35.8 41.2 59.3

90th Percentile 175.2 180.2 179.4 209.8 234.1 225.8 115.7 100.6 94.2 76.6 73.7 114.3

Average 87.52 102.79 96.03 111.49 118.93 103.05 61.17 40.88 39.19 31.67 32.31 53.78

0

50

100

150

200

250M

on

thly

Rai

nfa

ll (m

m)

Local Rainfall Distribution


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Figure 5.2 Mean monthly S-Pan evaporation values for the study area.

5.4 Available Data

5.4.1 Dam Capacities and Areas

The capacities and areas of the various impoundments are indicated in Table 5.2.

Table 5.2 Dam capacities used in the modelling

Facility Capacity (m3)

River Dam 3000

Mfolozi New Dam 3000

Pit A 400 000

Pit A RWD 1 4000

Pit A RWD 2 4000

Myenge Dam 1 49 000

Myenge Dam 2 202 780

Plant Header Dam 3170

North Pit RWD 5000

Plant PCD 4000

Platform PCD 12000

Workshop PCD 1 5000

Workshop PCD 2 5000

Settling ponds 1, 2, 3 and 4 16 827


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5.4.2 Pumping Capacities

Data were obtained from Somkhele Mine in the form of flow monitoring data. The records

were obtained from the following spreadsheets provided by the client (see Appendix A for

these):

• Water Usage spread sheets:

o Plant Usage Volumes (December 2014 to March 2017)(Annual average: 1 439

160 m3/annum) ;

o Pit A Return (December 2014 to March 2017)( 949 846m3/annum).

5.5 Results

The simulated mean mine water balances during the life of the mine are presented as follows

(m3/month):

• Average yearly mine water balance is shown in Figure 5.1;

• Wet season mine water balance is shown in Figure 5.2, and

• Dry season mine water balance is shown in Figure 5.3.


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Figure 5.1 Simulated average annual mine water balance

Abstraction 735720 m3/a 1 2 River Dam 735720 m3/a

735 720 735 720

Abstraction from Mfolozi River 735720 m3/a Myenge Dam 2 734379 m3/a

Rainfall 2166 m3/a 737 886 737 886 Evaporation 3507 m3/a

2 24Rainfall 2166 m3/a Evaporation 2166 m3/a

2 166 2 166

North Pit Dewatering 59400 m3/a 3 4 Dust Supression 57528 m3/a

Rainfall 3024 m3/a Evaporation 4897 m3/a

62 424 62 424

North Pit Return Water 57528 m3/a 4 Dust Supression 57528 m3/a

57 528 57 528

Rainfall 241920 m3/a 5 3 North Pit Return Water Dam 59400 m3/a

GW Ingress 209200 m3/a Evaporation 391720 m3/a

451 120 451 120

Pit A Slurry recovery 927563 m3/a 8,9 15-18 Settling Ponds 1,2,3,4 924110 m3/a


933 140 933 140

Slurry from plant 1,2,3 949846 m3/a 10 8,9 Pit A Return Water Dams 927563 m3/a


985 831 985 831

Pit Dewatering BDE 33400 m3/a 11 Dust Supression 124972 m3/a

Myenge 1 91572 m3/a

124 972 124 972

Rainfall 69120 m3/a 13 11 Dust Supression Area 2 33400 m3/a

GW Ingress 76200 m3/a Evaporation 111920 m3/a

145 320 145 320

Water From Platform PCD 6650 m3/a 14 15-18 Settling Ponds 1,2,3,4 0 m3/a

Rainfall 69120 m3/a Seepage 28000 m3/a

Settling Ponds 1,2,3,4 206785 m3/a 282 555 282 555 Dust Suppression 91572 m3/a

Evaporation 43439 m3/a

Spillage 119544 m3/a

Water From Myenge 1 0 m3/a 15-18 23 Plant Header Dam 741377 m3/a

Plant PCD 26753 m3/a Evaporation 20869 m3/a

Rainfall 12888 m3/a 969 031 969 031 Overflow to Myenge 1 206785 m3/a

Platform PCD 0 m3/a

Pit A return Water 924110 m3/a

Discard Dump Runoff 5280 m3/a

Runoff from dirty water catchment 12000 m3/a 19 15-18 Myenge 1 6650 m3/a


20 640 20 640

Stockpile Runoff 8000 m3/a 20 15-18 Settling Ponds 1,2,3,4 26753 m3/a

PLANT RUNOFF 20000 m3/a Evaporation 3260 m3/a

Rainfall 2013 m3/a 30 013 30 013

Rainfall 17280 m3/a 21 Evaporation 12000 m3/a

15-18 Settling Ponds 1,2,3,4 5280 m3/a

17 280 17 280

PLANT HEADER DAM 740130 m3/a 22 20 Plant Runoff into Plant PCD 20000 m3/a

Myenge 2 699030 Moisture in product 224657 m3/a

1 439 160 1 439 160 10 Moisture in Slurry to Pit A 949846 m3/a

Moisture in Discard 244657 m3/a

Settling Ponds 18,17,16,15 741377 m3/a 23 22 Plant 1,2,3 740130 m3/a


Rainfall 2013 m3/a 743 390 743 390

WATER FROM RIVER DAM 734379 m3/a 24 14 Plant Header Dam 699030 m3/a


776 300 776 300

Rainfall 30240 m3/a 25 19 Runoff to Platform PCD 0 m3/a


30 240 30 240

Rainfall 17280 m3/a 26 Evaporation 17280 m3/a

17 280 17 280

Rainfall 2765 m3/a 27,28 Settling Ponds 1,2,3,4 0 m3/a


2 765 2 765

Runoff 1217 m3/a Evaporation 5 596 m3/a

GW Ingress 10743 m3/a Dust Supression 6 364 m3/a

11960 11 960

IN 8576722.1 OUT 8576722.1

Notes

Mean Annual Precipitation 864 mm2

Mean Annual Evaporation 1399 mm2 0

SOMKHELE ANTHRACITE MINE WATER BALANCE

ANNUAL WATER BALANCE

IN OUT

PLANT 1,2,3

DUST SUPPRESION AREA 1


PIT A

PIT A RETURN WATER DAM1&2

RoM STOCKPILE

SETTLING PONDS 1,2,3,4

PLANT POLLUTION CONTROL DAM

WORKSHOP POLLUTION CONTROL DAMS

PLATFORM POLLUTION CONTROL DAM

MFOLOZI ABSTRACTION

STOCKPILES

MFOLOZI NEW DAM

MYENGE 2

MYENGE 1

PLANT HEADER DAM

NORTH PIT RETURN WATER DAM

NORTH PIT DE-WATERING

PITS BDE DEWATERING

DISCARD DUMP

RIVER DAM

KWALUHLANGA RWD


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Figure 5.2 Simulated wet season mine water balance

Abstraction 61 310 m3/m 1 2 River Dam 61 310 m3/m

61 310 61 310

Abstraction from Mfolozi River 61 310 m3/m Myenge 2 60 916 m3/m

Rainfall 25 m3/m 61 335 61 335 Evaporation 418 m3/m

2 24Rainfall 295.826 m3/m Evaporation 296 m3/m

296 296

North Pit Dewatering 3 741 m3/m 3 4 Dust Supression 3 570 m3/m

Rainfall 413 m3/m Evaporation 584 m3/m

4 154 4 154

North Pit Return Water 3 570 m3/m 4 Dust Supression 3 570 m3/a

3 570 3 570

Rainfall 33 040 m3/a 5 3 North Pit Return Water Dam 3 741 m3/m

GW Ingress 17 433 m3/a Evaporation 46 732 m3/m

50 473 50 473

Pit A Slurry recovery 119 104 m3/m 8,9 15-18 Settling Ponds 1,2,3,4 102 762 m3/m

Rainfall 762 m3/m Evaporation 1 077 m3/m

119 866 119 866 Dust Suppression 16026 m3/m

Slurry from plant 1,2,3 121 141 m3/m 10 8,9 Pit A Return Water Dams 119 104 m3/m

Rainfall 4 915 m3/m Evaporation 6 951 m3/m

126 056 126 056

Pit Dewatering BDE 2 438 m3/m 11 Dust Supression 10 069 m3/a

Myenge 1 7 631 m3/m

10 069 10 069

Rainfall 9 440 m3/m 13 11 Dust Supression Area 2 2 438 m3/m

GW Ingress 6 350 m3/m Evaporation 13 352 m3/m

15 790 15 790

Water From Platform PCD 511 m3/m 14 15-18 Settling Ponds 0 m3/m

Rainfall 3663.9 m3/m Seepage 2 333 m3/m

Settling Ponds 1,2,3,4 47 825 m3/m 52 000 52 000 Dust suppression 7 631 m3/m

Evaporation 5182.245 m3/m

Spillage 36853 m3/m

Water From Myenge 1 0 m3/m 15-18 23 Plant Header Dam 56 427 m3/m

Plant PCD 2 219 m3/m Evaporation 2 490 m3/m

Rainfall 1 760 m3/m 106 742 106 742 Overflow to Myege 1 47 825 m3/m

Pit A return Water 102 762 m3/m

Discard Dump Runoff 0 m3/m

Runoff from dirty water catchment 1 000 m3/m 19 15-18 Myege Dam 1 511 m3/m

Rainfall 1 180 m3/m Evaporation 1 669 m3/m

2 180 2 180

Stockpile Runoff 667 m3/m 20 15-18 Settling Ponds 1,2,3,4 2 219 m3/m

PLANT RUNOFF 1 667 m3/m Evaporation 389 m3/m

Rainfall 275 m3/m 2 608 2 608

Rainfall 2 360 m3/m 21 Evaporation 2 360 m3/m

15-18 Settling Ponds 1,2,3,4 0 m3/m

2 360 2 360

PLANT HEADER DAM 119 930 m3/m 22 20 Plant Runoff into Plant PCD 1 667 m3/m

Myege 2 63 617 m3/m Moisture in product 29 536 m3/m

183 547 183 547 10 Moisture in Slurry to Pit A 121 141 m3/m

Moisture in Discard 31 203 m3/m

Settling Ponds 18,17,16,15 56 427 m3/m 23 22 Plant 1,2,3 119 930 m3/m

Myenge 2 63 617 m3/m Evaporation 389 m3/m

Rainfall 275 m3/m 120 319 120 319

WATER FROM NEW RIVER DAM 60 916 m3/m 24 14 Plant Header Dam 63 617 m3/m

Rainfall 9218.2208 m3/m Evaporation 6517.376 m3/m

70 134 70 134

Rainfall 4 130 m3/m 25 19 Runoff to Platform PCD 0 m3/m

Evaporation 4 130 m3/m

4 130 4 130

Rainfall 2 360 m3/m 26 Evaporation 2 360 m3/m

2 360 2 360

Rainfall 378 m3/m 27,28 Settling Ponds 1,2,3,4 0 m3/m

Evaporation 378 m3/m

378 378

Runoff 189 Evaporation 668 m3/m

GW Ingress 5 943 m3/m 6 132 6 132 Dust Supression 5464 m3/m

IN 1005810 OUT 1005810

Notes

Mean Monthly Precipitation 118 mm2

Mean Monthly Evaporation 167 mm2 0


WET SEASON WATER BALANCE

IN OUT

PLANT 1,2,3



PIT A


RoM STOCKPILE





MFOLOZI ABSTRACTION

STOCKPILES

MFOLOZI NEW DAM

MYENGE 2

MYENGE 1

PLANT HEADER DAM



PITS BDE DEWATERING

DISCARD DUMP

RIVER DAM

KWALUHLANGA RWD


16-1243 4 May 2017 Page 16

Figure 5.3 Simulated dry season mine water balance

Abstraction 61310 m3/m 1 2 River Dam 61310 m3/m

61 310 61 310

Abstraction from Mfolozi River 61310 m3/m Myenge 2 61150 m3/m

Rainfall 7 m3/m 61 317 61 317 Evaporation 167 m3/m

2 24Rainfall 79 m3/m Evaporation 79 m3/m

79 79

North Pit Dewatering 7678 m3/m 3 4 Dust Supression 7556 m3/m


7 789 7 789

North Pit Return Water 7556 m3/m 4 Dust Supression 7556 m3/a

7 556 7 556

Rainfall 8865 m3/a 5 3 North Pit Return Water Dam 7678 m3/m

GW Ingress 17433 m3/a Evaporation 18620 m3/m

26 298 26 298

Pit A Slurry recovery 77704 m3/m 8,9 15-18 Settling Ponds 1,2,3,4 61453 m3/m


77 908 77 908 Dust Suppression 16026 m3/m

Slurry from plant 1,2,3 79155 m3/m 10 8,9 Pit A Return Water Dams 77704 m3/m


80 474 80 474

Pit Dewatering BDE 3563 m3/m 11 Dust Supression 9298 m3/a

Myenge 1 5735 m3/m

9 298 9 298

Rainfall 2533 m3/m 13 11 Dust Supression Area 2 3563 m3/m

GW Ingress 6350 m3/m Evaporation 5320 m3/m

8 883 8 883

Water From Plant PCD 2252 m3/m 14 15-18 Settling Ponds 1,2,3,4 0 m3/m

Rainfall 983 m3/m Seepage 2333 m3/m

Settling Ponds 1,2,3,4 6898 m3/m 10 133 10 133 Dust Suppression 5735 m3/m


Spillage 0 m3/m

Water From Myenge 1 0 m3/m 15-18 23 Plant Header Dam 56939 m3/m

Plant PCD 2252 m3/m Evaporation 992 m3/m

Rainfall 472 m3/m 64 829 64 829 Overflow to Myenge 1 6898 m3/m

Platform PCD 652 m3/m

Pit A return Water 61453 m3/m

Discard Dump Runoff 0 m3/m

Runoff from dirty water catchment 1000 m3/m 19 15-18 Myenge 1 652 m3/m


1 317 1 317

Stockpile Runoff 667 m3/m 20 15-18 Settling Ponds 1,2,3,4 2252 m3/m

PLANT RUNOFF 1667 m3/m Evaporation 155 m3/m

Rainfall 74 m3/m 2 407 2 407

Rainfall 633 m3/m 21 Evaporation 633 m3/m

15-18 Settling Ponds 1,2,3,4 0 m3/m

633 633

PLANT HEADER DAM 56858 m3/m 22 20 Plant Runoff into Plant PCD 1667 m3/m

Myenge 2 63074 Moisture in product 18722 m3/m

119 932 119 932 10 Moisture in Slurry to Pit A 79155 m3/m

Moisture in Discard 20388 m3/m

Settling Ponds 18,17,16,15 56939 m3/m 23 22 Plant 1,2,3 56858 m3/m


Rainfall 74 m3/m 57 013 57 013

WATER FROM RIVER DAM 61150 m3/m 24 14 Plant 63074 m3/m


64 823 64 823

Rainfall 1108 m3/m 25 19 Runoff to Platform PCD 652 m3/m


1 108 1 108

Rainfall 633 m3/m 26 Evaporation 633 m3/m

633 633

Rainfall 101 m3/m 27,28 Settling Ponds 1,2,3,4 0 m3/m


101 101

Runoff 51 m3/m Evaporation 266 m3/m

GW Ingress 9581 m3/m 9 632 9 632 Dust Supression 9366 m3/m

IN 673473 OUT 673473.05

Notes

Mean Monthly Precipitation 32 mm2

Mean Monthly Evaporation 67 mm2 0


DRY SEASON WATER BALANCE

IN OUT

PLANT 1,2,3



PIT A


RoM STOCKPILE





MFOLOZI ABSTRACTION

STOCKPILES

MFOLOZI NEW DAM

MYENGE 2

MYENGE 1

PLANT HEADER DAM



PITS BDE DEWATERING

DISCARD DUMP

RIVER DAM

KWALUHLANGA RWD


16-1243 4 May 2017 Page 17

6 CONCLUSIONS

The following conclusions can be made as a result of this study:

• A static water balance was created using Excel spreadsheets for the mining operations

at Somkhele Mine. This model is based on both data provided by the mine, as well as

consultant experience;

• The main source of water for the system is the Mfolozi River, amounting to 735 720

m3 per annum.

• The majority of water lost from the system is through the process plant.

• There is an issue with spillage at Myenge Dam 1 during the wet season.

• The model was calibrated using recorded data for several components of the mine,

and the calibration was largely satisfactory.

7 RECOMMENDATIONS

The following recommendations can be made as a result of this study:

• The monitoring network should be upgraded and extended to increase the knowledge

of the mine water system. It is recommended that the focus also placed on:

o The water levels in the various dams and pits;

o The transfer of water between PCDs, Water Supply Dams (Myenge 1 and 2,

River Dam and Settling ponds 1, 2, 3 and 4) and the Plant Header Dam.

o During the wet season, more water from the Settling ponds needs to be used

to minimise spillage from Myenge Dam 1.


16-1243 4 May 2017 Page 18

8 REFERENCES

• Schulze RE (1995). Hydrology and Agrohydrology: A text to accompany the ACRU 3.0

Agrohydrological Modelling System. Water Research Commission, Pretoria, Report

TT69/95, 1995.

• Smithers JC and Schulze RE (2002). Design Rainfall Estimation Programme (2002).

Rainfall Statistics for Design Flood Estimation in South Africa, WRC Project K5/1060.

• WRC. (2012). Surface Water Resources of South Africa. Water Research Commission.

• DWA. (2006b). Best Practice Guidelines for Water Resources Protection in the South

African Mining Industry. BPG G2: Water and Salt Balances. Pretoria: DWA.


16-1243 4 May 2017 Page 19

APPENDIX A:

Available Data for use in the water balance

Water Usage spread sheets:

o Plant Usage Volumes (December 2015 to July 2011)

Date

Plant 1 water

consumption

for the month

Plant 2 water

consumption

for the month

Plant 3 water

consumption

for the month

m³ m³ m³

2014/12/29 36850 46500 36580

2015/01/31 36850 46500 36580

2015/02/28 33284 42000 33040

2015/03/30 36850 46500 36580

2015/04/30 36850 46500 36580

2015/05/21 11887 15000 11800

2015/05/31 35661 45000 35400

2015/06/29 36850 46500 36580

2015/07/31 36850 46500 36580

2015/08/31 35661 45000 35400

2015/09/29 36850 46500 36580

2015/10/29 35661 45000 35400

2015/11/27 27340 34500 27140

2015/12/18 28529 36000 28320

2016/01/05 32095 40500 31860

2016/01/31 34079 43500 34807

2016/02/28 37061 46500 36580

2016/04/04 36680 43714 36411

2016/05/02 35587 46628 35535

2016/06/02 34108 41878 34522

2016/07/08 35469 45931 36521

2016/08/01 35460 43375 35058

2016/08/29 34781 43889 35234

2016/09/29 35692 44863 31195

2016/10/28 36269 42269 35776

2016/11/27 31754 40681 33930

2016/12/27 34374 43152 30920

2017/01/26 27593 35294 24665

2017/02/25 36850 46500 36580

2017/03/27 35661 45000 35400

2017/04/26 36850 46500 36580

2017/05/26 35661 45000 35400

Appendix 19 - gcs-sa.biz · Appendix 19 WATER BALANCE. 63 Wessel Road, Rivonia, 2128 PO Box 2597,...

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Transcript of Appendix 19 - gcs-sa.biz · Appendix 19 WATER BALANCE. 63 Wessel Road, Rivonia, 2128 PO Box 2597,...