ATMOSPHERIC IMPACT REPORT: MORTIMER SMELTER...Platinum District Municipality in the North West Province. RPM holds an Atmospheric Emissions Licence (AEL) for its operations and is

Address: 480 Smuts Drive, Halfway Gardens | Postal: P O Box 5260, Halfway House, 1685 Tel: +27 (0)11 805 1940 | Fax: +27 (0)11 805 7010

www.airshed.co.za

ATMOSPHERIC IMPACT REPORT:

MORTIMER SMELTER

Project done on behalf of: Anglo American Platinum

Report Compiled by: N Grobler

Report No: 17AAP01-02 | Date: November 2018

Project Manager: H Liebenberg-Enslin

Atmospheric Impact Report: Mortimer Smelter

Report No.: 17AAP02-02 i

Report Details

Project Name Atmospheric Impact Report: Mortimer Smelter

Client Anglo American Platinum

Report Number 17AAP02-02

Report Version Draft

Date November 2018

Prepared by Nick Grobler, BEng (Chem), BEng (Hons) (Env) (University of Pretoria)

Reviewed by Hanlie Liebenberg-Enslin, PhD (University of Johannesburg)

Notice

Airshed Planning Professionals (Pty) Ltd is a consulting company located in Midrand,

South Africa, specialising in all aspects of air quality, ranging from nearby

neighbourhood concerns to regional air pollution impacts as well as noise impact

assessments. The company originated in 1990 as Environmental Management

Services, which amalgamated with its sister company, Matrix Environmental

Consultants, in 2003.

Declaration

Airshed is an independent consulting firm with no interest in the project other than to

fulfil the contract between the client and the consultant for delivery of specialised

services as stipulated in the terms of reference.

Copyright Warning

Unless otherwise noted, the copyright in all text and other matter (including the manner

of presentation) is the exclusive property of Airshed Planning Professionals (Pty) Ltd. It

is a criminal offence to reproduce and/or use, without written consent, any matter,

technical procedure and/or technique contained in this document.

Revision Record

Version Date Section(s) Revised Summary Description of Revision(s)

Draft November 2018


Report No.: 17AAP02-02 ii

Preface

Anglo American Platinum’s (AAP) subsidiary, Rustenburg Platinum Mines Limited (RPM), owns and operates the

Mortimer Smelter to the west of the town of Northam, in the Moses Kotane Local Municipality and Bojanala

Platinum District Municipality in the North West Province.

RPM holds an Atmospheric Emissions Licence (AEL) for its operations and is required to comply with the Minimum

Emission Standards (MES) published in terms of Section 21 of the National Environment Management: Air Quality

Act, No. 39 of 2004 (NEM:AQA). RPM applied for the postponement of the “Existing Plant” Minimum Emission

Standards (MES) (which came into effect on 1 April 2015) and was granted a postponement for compliance with

the 2015 MES.

The Listed Activities and associated MES, identified in terms of Section 21 of NEM:AQA, now require the Mortimer

Smelter operations to comply with the “New Plant‟ MES by 01 April 2020. RPM plans to install abatement

equipment (a Wet Sulfuric Acid Plant – WSA) to mitigate Sulphur Dioxide (SO2) emissions to comply with the

abovementioned New Plant MES. The investment cost of this plant is approximately R1 billion, and will result in a

96 % reduction of SO2 once the WSA plant is fully operational. The installation of the abatement equipment is

expected to be completed and fully ramped up by March 2025 consequently, RPM proposes to apply for

postponement, until end of March 2025, of the New Plant MES.

During construction of the WSA abatement equipment, the current furnace and off-gas train require sealing to

achieve the SO2 concentrations required by the acid plant. The sealing will limit the amount of ingress air into the

off-gas train, reducing the volumetric flow rate of the off-gas. Although the mass emission rate of SO2 will remain

the same as before the sealing, the lower volumetric flow rate of the off-gas is likely to cause an increase in SO2

concentrations. RPM, therefore, proposes to apply for a higher monthly average SO2 concentration limit of

52 000 mg/Nm³ at Mortimer Smelter during the construction/commissioning period, until end of March 2025.

In support of the submissions and to fulfil the requirements for these applications stipulated in NEMAQA and the

MES, air quality studies are required to substantiate the motivations for the extension.

Airshed Planning Professionals (Pty) Ltd (hereafter referred to as Airshed) was appointed by AAP to provide

independent and competent services for the compilation of an Atmospheric Impact Report as set out in the

Regulations Prescribing the format of the Atmospheric Impact Report, 2013, published under Government Notice

747 in Government Gazette 36904 of 11 October 2013 and detailing the results of the dispersion modelling

simulation, conducted in accordance with the Regulations Regarding Air Dispersion Modelling under Government

Notice R533, Government Gazette 37804 of 11 July 2014.


Report No.: 17AAP02-02 iii

Table of Contents

Enterprise Details ........................................................................................................................................... 1

Enterprise Details .................................................................................................................................. 1

Location and Extent of the Plant ............................................................................................................ 1

Description of Surrounding Land Use (within 5 km radius) .................................................................... 2

Atmospheric Emission Licence and other Authorisations ...................................................................... 3

Nature of the Process ..................................................................................................................................... 3

Listed Activities ...................................................................................................................................... 3

Process Description ............................................................................................................................... 4

Unit Processes ...................................................................................................................................... 5

Technical Information ..................................................................................................................................... 8

Raw Materials Used and Production Rates ........................................................................................... 8

Production Rates ................................................................................................................................... 8

Appliances and Abatement Equipment Control Technology .................................................................. 8

Atmospheric Emissions .................................................................................................................................. 9

Point Source Parameters ...................................................................................................................... 9

Point Source Maximum Emission Rates during Normal Operating Conditions.................................... 10

Furnace Main Stack Emission Estimation ....................................................................................... 11

Flash Drier Emission Estimation ..................................................................................................... 13

Future WSA Stack Emission Estimation ......................................................................................... 13

Fugitive Emissions ............................................................................................................................... 13

Furnace Building ............................................................................................................................. 15

Vehicle Entrainment ........................................................................................................................ 15

Wind Erosion ................................................................................................................................... 16

Material Handling ............................................................................................................................ 16

Crushing .......................................................................................................................................... 16

Vehicle Exhaust .............................................................................................................................. 16

Emission Summary .............................................................................................................................. 17

Emergency Incidents ........................................................................................................................... 17

Impact of Enterprise on the Receiving Environment .................................................................................... 19

Analysis of Emissions’ Impact on Human Health ................................................................................ 19

Study Methodology ......................................................................................................................... 19


Report No.: 17AAP02-02 iv

Legal Requirements ........................................................................................................................ 22

Atmospheric Dispersion Processes ................................................................................................. 26

Atmospheric Dispersion Potential ........................................................................................................ 30

Surface Wind Field .......................................................................................................................... 30

Temperature .................................................................................................................................... 32

Air Quality Monitoring data .................................................................................................................. 33

Dispersion Modelling Results .............................................................................................................. 37

Simulated SO2 Concentrations ........................................................................................................ 38

Simulated PM10 Concentrations ...................................................................................................... 43

Simulated NO2 Concentrations........................................................................................................ 45

Comparison of Measured and Modelled Concentrations ................................................................ 48

Conclusion ...................................................................................................................................... 49

Analysis of Emissions’ Impact on the Environment ............................................................................. 50

Effects of Particulate Matter on Animals ......................................................................................... 50

Effects of SO2 on Plants and Animals ............................................................................................. 51

Dust Effects on Vegetation .............................................................................................................. 51

Complaints ................................................................................................................................................... 52

Current Or Planned Air Quality Management Interventions ......................................................................... 52

Compliance And Enforcement History.......................................................................................................... 53

Additional Information ................................................................................................................................... 53

Annexure A – Declaration of Accuracy of Information .................................................................................. 54

Annexure B – Declaration of Independence ................................................................................................. 55

Annexure C – Excerpts from 2017 Isokinetic Sampling by Future Projects ................................................. 56

Annexure D – Information Required in the Air Dispersion Modelling Report as Per Code of Conduct (DEA,

2014) ..................................................................................................................................................................... 58

Annexure E – References ............................................................................................................................ 62

Annexure E – List of Electronic Files Submitted with the Report .................................................................. 64


Report No.: 17AAP02-02 v

List of Tables

Table 1-1: Enterprise details ................................................................................................................................... 1

Table 1-2: Contact details of responsible person .................................................................................................... 1

Table 1-3: Location and extent of the plant ............................................................................................................. 1

Table 2-1: Listed activities ....................................................................................................................................... 4

Table 2-2: List of unit processes considered listed activities under NEMAQA ........................................................ 5

Table 2-3: List of non-listed activity unit processes ................................................................................................. 5

Table 3-1: Raw materials used ............................................................................................................................... 8

Table 3-2: Production Rates ................................................................................................................................... 8

Table 3-3: Appliances and abatement equipment control technology ..................................................................... 8

Table 4-1: Point source parameters ........................................................................................................................ 9

Table 4-2: Point source emission rates during normal operating conditions ......................................................... 10

Table 4-3: Point Source Maximum Emission Rates during Start-up, Maintenance and/or Shut-down .................. 10

Table 4-4: Past Actual (2017) and Future (with sealing, prior to WSA plant operation) Electric Furnace Stack

Parameters ........................................................................................................................................................... 11

Table 4-5: Isokinetic sampling SO2 emission rates – 2014 to 2017 (see Annexure E for data sources) .............. 12

Table 4-6: Fugitive emission sources .................................................................................................................... 14

Table 4-7: Paved road source emission parameters ............................................................................................. 15

Table 4-8: Material Handling Throughputs ............................................................................................................ 16

Table 4-9: Summary of Emissions from the Mortimer Smelter Operations ........................................................... 17

Table 5-1: Summary description of CALPUFF/CALMET model suite with versions used in the investigation ...... 22

Table 5-2: National Ambient Air Quality Standards for SO2, PM10 and NO2 .......................................................... 23

Table 5-2: Listed Activity Subcategory 4.1 ............................................................................................................ 24

Table 5-4: Listed Activity Subcategory 4.16: Smelting and Converting of Sulphide Ores ..................................... 24

Table 5-3: Definition of vegetation cover for different developments (US EPA 2005) ........................................... 29

Table 5-4: Summary of 2014 to 2017 Ambient Monitoring Results ....................................................................... 34

Table 5-5: Discreet Receptor Locations with Coordinates .................................................................................... 37

Table 5-6: Simulated SO2 concentration at discreet receptor locations – current operations with the Electric Furnace

Stack operating at 52 000 mg/Nm³. ...................................................................................................................... 38

Table 5-7: Simulated SO2 concentration at discreet receptor locations – future operations. ................................ 40

Table 5-8: Simulated PM10 concentration at discreet receptor locations – current and future operations. ............ 43

Table 5-9: Simulated NO2 concentration at discreet receptor locations – current and future operations. ............. 46


Report No.: 17AAP02-02 vi

List of Figures

Figure 1-1: Mortimer location with sensitive receptors and the closest ambient monitoring stations shown (10 km

radius). .................................................................................................................................................................... 2

Figure 1-2: Mortimer Smelter location with topography and major towns and significant emission sources shown–

50 km radius ........................................................................................................................................................... 3

Figure 2-1: Site Layout Map .................................................................................................................................... 4

Figure 2-2: Process flow chart indicating inputs, outputs and emissions at the site of works, including points of

emissions. ............................................................................................................................................................... 6

Figure 2-3: Proposed changes to the off-gas train to decrease gas volume prior to treatment in the acid plant. .... 7

Figure 4-1: Frequency distribution of current and future SO2 concentrations in the Electric Furnace stack......... 13

Figure 4-2: Source Contributions – SO2 Emissions ............................................................................................... 18

Figure 4-3: Source Contributions – PM10 Emissions ............................................................................................. 18

Figure 4-4: Source Contributions – NOx Emissions ............................................................................................... 18

Figure 5-1: The basic study methodology followed for the assessment ................................................................ 20

Figure 5-2: Plume buoyancy ................................................................................................................................. 28

Figure 5-3: Period, day- and night-time wind rose for the period 2014 – 2016 (CALMET Processed WRF and On-

site Data). .............................................................................................................................................................. 31

Figure 5-4: Seasonal wind roses for the period 2014 – 2016 (CALMET Processed WRF and On-site Data). ...... 31

Figure 5-5: Monthly average temperature (°C) profile for the period 2014 to 2016 .............................................. 32

Figure 5-6: Background (median) concentrations recorded at the four APP monitoring stations during 2017 ...... 33

Figure 5-7: Annual average SO2 concentration recorded at the four AAP monitoring stations during 2017. ........ 34

Figure 5-8: 99th Percentile daily SO2 concentrations at the four AAP monitoring stations (no exceedances of the

NAAQS limit value of 125 µg/m³ for SO2 were recorded during 2017) ................................................................. 35

Figure 5-9: Hourly exceedances of the NAAQS limit value for SO2 recorded at the four AAP monitoring stations

during 2017. .......................................................................................................................................................... 35

Figure 5-10: Annual average PM10 concentration recorded at the four AAP monitoring stations during 2017 ...... 36

Figure 5-11: Daily exceedances of the NAAQS limit value for PM10 recorded at the four AAP monitoring stations

during 2017. .......................................................................................................................................................... 36

Figure 5-12: Simulated annual average SO2 concentrations due to current operations with the Electric Furnace

Stack operating at an average SO2 concentration of 52 000 mg/Nm³. .................................................................. 39

Figure 5-13: Simulated 99th percentile daily SO2 concentrations due to current operations with the Electric Furnace

Stack operating at an average SO2 concentration of 52 000 mg/Nm³. .................................................................. 39

Figure 5-14: Simulated 99th percentile hourly SO2 concentrations due to current operations with the Electric

Furnace Stack operating at an average SO2 concentration of 52 000 mg/Nm³. ................................................... 40

Figure 5-15: Simulated annual average SO2 concentrations due to future operations ......................................... 41

Figure 5-16: Simulated 99th percentile daily SO2 concentrations due to future operations .................................. 42

Figure 5-17: Simulated 99th percentile hourly SO2 concentrations due to future operations ................................ 42

Figure 5-18: Simulated annual average PM10 concentrations due to current operations ..................................... 44

Figure 5-19: Simulated 99th percentile daily PM10 concentrations due to current operations ............................... 44

Figure 5-20: Simulated annual average PM10 concentrations due to future operations ....................................... 45

Figure 5-21: Simulated 99th percentile daily PM10 concentrations due to future operations ................................. 45


Report No.: 17AAP02-02 vii

Figure 5-22: Simulated annual average NO2 concentrations due to current operations ...................................... 46

Figure 5-23: Simulated 99th percentile hourly NO2 concentrations due to current operations .............................. 47

Figure 5-24: Simulated annual average NO2 concentrations due to future operations ........................................ 47

Figure 5-25: Simulated 99th percentile hourly NO2 concentrations due to future operations ................................ 48

Figure 5-26: Modelled vs Measured Annual Average SO2 Concentrations at the AAP Monitoring Stations. ....... 49

Figure 5-27: Modelled vs Measured 99th Percentile Daily SO2 Concentrations at the AAP Monitoring Stations. . 49

Figure 5-28: Modelled vs Measured 99th Percentile Hourly SO2 Concentrations at the AAP Monitoring Stations.

.............................................................................................................................................................................. 49


Report No.: 17AAP02-02 1

Atmospheric Impact Report

ENTERPRISE DETAILS

Enterprise Details

The details of the Mortimer Smelter operation are summarised in Table 1-1. The contact details of the responsible

person are provided in Table 1-2. Details regarding the location, surrounding land use and communities are shown

in Table 1-3 and Figure 1-1 to Figure 1-2.

Table 1-1: Enterprise details

Enterprise Name Rustenburg Platinum Mines Limited

Trading as Rustenburg Platinum Mines Limited (Mortimer Smelter)

Type of Enterprise Proprietary Limited Company

Company Registration Number 1946/022452/06

Registered Address & Postal Address Private Bag X351, Swartklip, 0370

Telephone Number (General) (014) 786 1269

Fax Number (General) (014) 591 4480

Industry Type/Nature of Trade Smelter, producing furnace matte suitable for further

processing by Waterval ACP

Land Use Zoning as per Town Planning Scheme Mining

Land Use Rights if Outside Town Planning Scheme N/A

Table 1-2: Contact details of responsible person

Responsible Person Sam Ngaka

Telephone Number (014) 786 1091

Cell Number 083 752 8846

Fax Number N/A

Email Address [email protected]

After Hours Contact Details 083 414 8475

Location and Extent of the Plant

Table 1-3: Location and extent of the plant

Physical Address of the Plant Portion of Turfbult 404 KQ, Swartklip

Coordinates of Approximate Centre of Operations North-south: 24° 41’ 47”

mailto:[email protected]



East-west: 27° 18’ 17”

Extent 0.565 km²

Elevation Above Sea Level 1036

Province North West Province

Metropolitan/District Municipality Bojanala Platinum District Municipality

Local Municipality Moses Kotane Local Municipality

Designated Priority Area Waterberg Bojanala Priority Area

Description of Surrounding Land Use (within 5 km radius)

Mortimer Smelter is located at the Union Mine Operations, approximately 17km to the west of Northam in the North-

West Province. Land use within the Union Mine boundary include mining and processing operations as well as

interspersed residential areas. Identified air quality sensitive receptors (Figure 1-1) within 10 km radius of Mortimer

Smelter include residential areas inside the Union Mine boundary (Swartklip town, Elafeni Single Accommodation

Village and Hlatini Single Accommodation Village) as well as residential areas outside the Union Mine boundary

(Matserre and Sefikile). Identified schools, hospitals and clinics within 10 km radius of Mortimer Smelter include

the Platinum Health Hospital and Laerskool Platina Primary located within the Union Mine boundary as well as the

Mantserre Primary School, Sefikile Primary School and Sefikile Clinic outside the Union Mine boundary.

Figure 1-1: Mortimer Smelter location with sensitive receptors and the closest ambient monitoring stations

shown (10 km radius).



Figure 1-2: Mortimer Smelter location with topography and major towns and significant emission sources

shown– 50 km radius

Atmospheric Emission Licence and other Authorisations

The following authorisations, permits and licences related to air quality management are applicable:

• Air Pollution Prevention Act (APPA) Registration Certificates:

o 349/1 (Smelter)

o 349/2 (Drying and Pelletizing Plant)

o 349/2 (Flash Dryer)

• Atmospheric Emission License: NWPG/MORTIMER/PAEL 4.1 & 4.16/NOV11

o Permanent AEL – Issued 19 October 2016 and valid until 30 October 2021

NATURE OF THE PROCESS

Listed Activities

A summary of listed activities currently undertaken at the Mortimer Smelter is provided in Table 2-1. The site layout

is shown in Figure 2-1.



Table 2-1: Listed activities

Category of Listed Activity Sub-category of the Listed Activity Description of the Listed Activity

Category 4: Metallurgical Industry Subcategory 4.1: Drying Drying of mineral solids including ore.

Category 4: Metallurgical Industry Subcategory 4.16: Smelting and

Converting of Sulphide Ores

Processes in which sulphide ores are

smelted, roasted, calcined or

converted.

Figure 2-1: Site Layout Map

Process Description

Filtering Process

Dewatering of various Platinum Group Metal (PGM) concentrate slurry feed streams delivered to the site, supplied

by both pipeline and slurry tankers.

Drying Process

A drying plant is used to dry various filtered concentrate materials to a bone dry product which is then fed into the

furnace. A baghouse filter is utilized as air pollution control equipment (APCE) for the control of particulate matter



emissions. Additional filtered concentrate is delivered to site by trucks, for subsequent processing through the

drying plant.

Smelting Process

The dried material from the drying process, together with other raw materials fluxes and recycle streams are

smelted in the furnace. The furnace (smelter) is a 51 MVA (nominally 38 MW) 6-in-line electric furnace. Current

APCE for the smelter is a four (4) field Electrostatic Precipitator (ESP) system.

Crushing Process

A primary and secondary crusher circuit is used to crush the furnace matte, a product from the smelting process,

to a -2mm product for delivery to the Anglo Converter Process at Waterval Smelter (ACP).

Unit Processes

Unit processes considered listed activities under the NEMAQA are summarised in Table 2-2. Other unit processes

that may result in atmospheric emissions which are not considered listed activities are summarised in Table 2-3.

The locations of the unit processes are shown in Figure 2-1.

Table 2-2: List of unit processes considered listed activities under NEMAQA

Name of the Unit

Process

Unit Process

Function

Batch or

Continuous

Process

Listed Activity Sub-category

Drying Process Drying of concentrate Continuous 4.1: Drying

Smelting Process Smelting of

concentrate Continuous

4.16: Smelting and Converting of Sulphide

Ores

Table 2-3: List of non-listed activity unit processes

Name of the Unit

Process Unit Process Function

Batch or

Continuous

Process

Filtering process Dewatering of concentrate slurry Batch

Crushing Process Crushing of furnace matte Batch

Future WSA Plant Future Wet gas Sulfuric Acid plant to produce high strength sulfuric acid from

SO2 released by the furnace. Continuous



Figure 2-2: Process flow chart indicating inputs, outputs and emissions at the site of works, including

points of emissions.



Figure 2-3: Proposed changes to the off-gas train to decrease gas volume prior to treatment in the acid

plant.



TECHNICAL INFORMATION

Raw material consumption and production rates are tabulated in Table 3-1 and Table 3-2 respectively. Pollution

abatement technologies employed at Mortimer Smelters’ listed activities, and technical specifications thereof, are

provided in Table 3-3.

Raw Materials Used and Production Rates

Table 3-1: Raw materials used

Raw Material Type Design Consumption Rate Rate Unit

Flash drier

Wet concentrate 50 900 Tonne/month

Coal (washed pea) 1 629 Tonne/month

Furnace

Dry concentrate 38 000 Tonne/month

Limestone 1 570 Tonne/month

Electrode paste 115 Tonne/month

Production Rates

Table 3-2: Production Rates

Product Type Design Production Rate Rate Unit

Matte 6 000 Tonne/month

Slag (by-product) 32 300 Tonne/month

Future H2SO4 40 Tonne/day

Appliances and Abatement Equipment Control Technology

Table 3-3: Appliances and abatement equipment control technology

Appliance Name Appliance Type / Description Appliance Function / Purpose

Flash Dryer Baghouse Bag house Dust Collection

Furnace ESP Electrostatic Precipitator Furnace Off Gas Dust Collection

Future WSA Plant Wet gas Sulfuric Acid Plant Furnace Off-gas SO2 reduction



ATMOSPHERIC EMISSIONS

The establishment of a comprehensive emission inventory formed the basis for the assessment of the air quality impacts from the Mortimer Smelter operations on the receiving

environment. Point source parameters used in the dispersion modelling simulations are shown in Table 4-1. Emission rates during normal operations are shown in Table 4-2

with a qualitative description of upset conditions in Table 4-3. The emission estimation techniques used to quantify emissions from each point source are described in Sections

4.2.1 to 4.2.3. Future emission sources when the WSA plant is operational are shown in italics in Table 4-1 and Table 4-2, these sources are not currently active but a dispersion

modelling scenario was included to simulate future impacts.

Point Source Parameters

Table 4-1: Point source parameters

Point

Source

Number

Point

Source

Name

Point Source

Coordinates

Height of

Release

above

Ground (m)

Height above

Nearby

Building (m)

Diameter at

Stack Tip or Vent

Exit (m)

Actual Gas Exit

Temperature

(°C)

Actual Gas

Volumetric Flow Rate

(m³/hr)

Actual Gas Exit

Velocity (m/s)

Type of

Emission

(Continuous

/Batch)

Mort FD Flash Dryer 24.9708 S

27.1435 E 50 ~20 1.4 103 106 200 17.3 Continuous

Mort EF Electric

Furnace

24.9730 S

27.1439 E 80 ~50 1.35 180 46 700 9.2 Continuous

Mort

WSA

Future WSA

Stack

~24.9707 S

~27.1424 E 60 ~43 1.2 80 ~52 200 ~12.8 Continuous



Point Source Maximum Emission Rates during Normal Operating Conditions

Table 4-2: Point source emission rates during normal operating conditions

Point

Source

Number

Point Source Name Pollutant

Name

Average Emission Rate

Emission Concentration

(mg/Nm3)

Averaging

Period

Emission Rate

(g/s)

Emission Rate

(t/a) Duration of Emission

Mort FD Flash Dryer

SO2 211 (2017 Sampling) 24-hours 3.6 114.4 Continuous

PM 597 (2017 Sampling) 24-hours 10.3 323.6 Continuous

NOx 254 (2017 Sampling) 24-hours 4.4 137.7 Continuous

Mort EF Electric Furnace

SO2

Variable

(See Section 4.2.1)

2017 Average 23 600

2019-2025 Average 52 000

30-days

Variable

(See Section 4.2.1)

Average 154

Variable

(See Section 4.2.1)

Average 4870

Continuous

PM 135 (2017 Sampling) 24-hours 1 31.6 Continuous

NOx 47 (2017 Sampling) 24-hours 0.3 11 Continuous

Mort

WSA Future WSA Stack

SO2 1 200 24-hours 11 185 Continuous

PM 50 24-hours 0.3 7.7 Continuous

NOx 61 24-hours 0.3 9.5 Continuous

Table 4-3: Point Source Maximum Emission Rates during Start-up, Maintenance and/or Shut-down

Process Description of Nature of Potential Abnormal Release (e.g. leakage, technology

outage, etc.)

Pollutant(s) Released Briefly Outline Emergency

Procedures

Start-up, shut down and

upset conditions

Variations in SO2 concentrations as well as off-gas volumetric flow rate during start-up,

shut down, and other upset conditions are reflected within the hourly emission profile

as described in Section 4.2.1.

SO2 None



Furnace Main Stack Emission Estimation

In order to account for variations in emission rates during normal and upset conditions, SO2 emissions from the

Electric Furnace stack were quantified using the continuously sampled hourly SO2 concentrations for 2017. The

2017 emission profile as described in Figure 2-3 was used to compile an hourly variable emission rate file (a

PTEMARB.dat file as required by the CALPUFF model) to include these variable emissions in the dispersion

modelling.

Both SO2 concentrations as well as off-gas volumetric flow rate during start-up, shut down, and other upset

conditions are reflected within the hourly emission profile. It should be noted that the reduction in the off-gas

volumetric flow rate will only result in an increase in emission concentrations (mg/Nm³) and not emission

rates, the average SO2 emission rate in grams per second will remain unchanged from the equivalent

operation without any sealing of the off-gas train. The resulting change in exit temperature and velocity are

unlikely to have any significant effect on plume buoyancy (as discussed in Section 5.1.3.1) as the decrease in

velocity will result in a lower plume buoyancy, while the increase in temperature will result in a more buoyant plume,

thus essentially cancelling each other out.

Calculated parameters for the 2017 emission profile as well as the 2019 to 2025 (with sealing but prior to WSA

plant operation) emission profile are shown in Table 4-4.

Table 4-4: Past Actual (2017) and Future (with sealing, prior to WSA plant operation) Electric Furnace Stack

Parameters

Parameter Past Actual (2017) Future Projected (before the

operation of the WSA Plant)

Average SO2 Concentration 23 600 mg/Nm³ 52 000 mg/Nm³

Average Volumetric Flow Rate 31 500 m³/h 24 000 m³/h

Average Normal Volumetric Flow Rate 23 600 Nm³/h 10 700 Nm³/h

Average Exit Temperature 181 °C 242 °C

Average Exit Velocity 6.2 m/s 4.7 m/s

Average SO2 Emission Rate 154 g/s 154 g/s

The frequency distribution of measured hourly SO2 concentrations in the Electric Furnace stack during 2017 follow

a normal distribution with an average of 23 600 mg/Nm³ and a standard deviation of 8 500 mg/Nm³. The frequency

of occurrence of very low (



Particulate matter emissions from the Electric Furnace stack were simulated as a constant emission rate of 1 g/s

based on isokinetic stack sampling conducted by Future Projects on 7 April 2017. A summary of the results from

the Emission Testing Report is included as Annexure C.

NOx emissions from the Electric Furnace stack were simulated as a constant emission rate of 0.3 g/s based on

isokinetic stack sampling conducted by Future Projects on 7 April 2017. A summary of the results from the Emission

Testing Report is included as Annexure C.

Table 4-5: Isokinetic sampling SO2 emission rates – 2014 to 2017 (see Annexure E for data sources)

Year Isokinetic sampling average SO2 emission rate (g/s)

2014 135 (SGS)

2015 88 (SGS)

2016 64 (SGS)

2017 154 (Future Projects)

Table 4-6: Summary of SO2 Emission Rates reported on the NAEIS system, 2015 to 2018

Source Year SO2 emission rate (kg/a)

Flash Dryer 1

2015 114 756

2016 68 591

2017 113 880

Main Stack

2015 2 407 549

2016 2 776 920

2017 4 870 560



Figure 4-1: Frequency distribution of current and future SO2 concentrations in the Electric Furnace stack.

Flash Drier Emission Estimation

PM, SO2 and NOx emission rates from the Flash Drier stack were based on isokinetic stack sampling conducted

by Future Projects on 6 April 2017. A summary of the results from the Emission Testing Report is included as

Annexure C.

Future WSA Stack Emission Estimation

Stack parameters and volumetric flow rates from the future WSA stack were based on design parameters as

described in the Air Quality Impact Assessment conducted by WSP in 2017 (WSP, 2017). PM and NOx emission

rates were conservatively assumed to remain unchanged from current emissions from the Electric Furnace stack.

In reality the new ESP as well as the acid plant will reduce the PM and with negligible increase in NOx emission

rates when compared to their current levels. It was assumed that the WSA plant will be effective in reducing SO2

concentrations to less than 1 200 mg/Nm³ (which the WSA is designed for).

Fugitive Emissions

In addition to point source process emissions, Mortimer Smelter operations also results in fugitive SO2 emissions

from the furnace building released during tapping and casting, as well as vehicle tailpipe emissions. Sources of



fugitive PM emissions from the Mortimer Smelter operations that were identified, quantified and included in the

dispersion modelling simulations include vehicle entrainment from on-site paved roads, wind erosion from

concentrate stockpiles and the slag dump, fugitive dust emissions from crushing, screening and materials handling

and vehicle exhaust emissions from vehicles operating on-site.

A summary of fugitive emission sources is given in Table 4-7. A detailed description of the parameters and

emissions estimation techniques used to quantify emissions from each of the fugitive emission sources is given in

the following sections.

Table 4-7: Fugitive emission sources

Emission

Source

Location

(SW corner)

Length

(m)

Width

(m) Pollutant

Emissions rate

(g/s)

Temporal

Variation

Furnace

building –

tapping and

casting

emissions

24.9728°S

27.1440°E 75 50

SO2 0.43 Dependent on

tapping and

casting

schedule,

wind direction

and wind

speed

PM 0.22

Vehicle

Entrainment

24.9743°S

27.1440°E

1144 Total

(Section

4.3.2)

10 PM 0.11

Dependent on

vehicle

movements,

vehicle loads

and vehicle

speeds

Wind Erosion

- Concentrate

24.9741°S

27.1444°E 100 80 PM 0.016 Heavily

dependent on

wind speed

and direction Wind Erosion

– Slag Dump

24.9701°S

27.1442°E 380 360 PM 0.33

Materials

Handling

24.9741°S

27.1444 °E 90 60 PM 0.0004

Dependent on

wind speed

and direction

Crushers -24.9729°S

27.1436°E 3 3 PM 0.0003

Dependent on

wind speed

and direction

Vehicle

Exhaust

24.9743°S

27.1440°E

1144 Total

(Section

4.3.2)

10

SO2 0.00014 Dependent on

vehicle

movements

and idling

times

PM 0.0002

NOx 0.004



Furnace Building

The ventilation rate of the furnace building was calculated based on the dimensions of the furnace building

(approximately 75m long by 50m wide by 25m high) and an estimated four volume changes per hour based on the

number of openings in the building walls. The average SO2 concentration (1.73 mg/m³) inside the furnace building

was estimated from SO2 concentrations recorded for occupational health at various location during 2017.

Fugitive PM emissions from the furnace building were calculated using the US EPA AP-42 Section 12.5 (Iron and

Steel Production) emission factors for charging, tapping and slagging in electric arc furnaces (0.0215 kg/tonne)

controlled by direct shell evacuation plus charging hood and the 2017 concentrate smelting rate

(320 860 tonnes/annum). A control efficiency of 90% was applied to account for the mitigating effect of the furnace

building on particulate emissions inside the building.

Vehicle Entrainment

Fugitive dust emissions from vehicle entrainment were calculated using the US EPA AP42 Section 13.2.1 (Paved

Roads) emission factor equation (Equation 4-1) for PM10. This equation relates the PM10 emission rate in grams

per vehicle kilometre travelled (g/VKT) to the silt loading (sL) of the road surface and the average weight (W) of

vehicles travelling on the road. An average silt content of 9.7 g/m² (given by the US EPA as the average of 48

samples taken at iron and steel production facilities) was assumed. The number of trips per day for each vehicle

type was calculated from the 2017 concentrate and coal consumption and matte production rates. A summary of

emissions from paved road sources at Mortimer Smelter is given in Table 4-8. The parameters for the future road

used for delivery of lime and acid to and from the new WSA plant was assumed to remain unchanged from the air

quality impact assessment conducted as part of the EIA for the WSA (WSP, 2017). Paved roads at Mortimer

Smelter are mitigated with sweepers, a 40% mitigation efficiency was therefore assumed. All roads were assumed

to be 10 metres wide.

𝑬 = 𝟎. 𝟔𝟐 (𝒔𝑳)𝟎.𝟗𝟏 × (𝑾)𝟏.𝟎𝟐 𝒈/𝑽𝑲𝑻 Equation 4-1

Table 4-8: Paved road source emission parameters

Road Average Vehicle

Weight (tonne)

Total Road

Length (m)

VKT/day Average trips

per day

Main Delivery Road 50 252 8.2 33

Coal and Concentrate Delivery Road 54 536 15.3 28

Matte Road 37 75 0.3 4

Future Acid and Lime Road 32 281 1.7 6



Wind Erosion

Wind erosion from the concentrate stockpiles as well as the slag dump (see Figure 2-1) was calculated using the

Australian NPI Emission Estimation Technique Manual for Mining single value emission factor of 0.2 kg/ha/h for

wind erosion from stockpiles at metalliferous mines. A 50% control efficiency was assumed due to the high

moisture content of both the received concentrate and the slag.

Material Handling

Fugitive dust emissions from material handling were estimated using the US EPA Section 13.2.4 (Aggregate

Handling and Storage Piles) emission factor equation (Equation 4.2) for material handling. This equation is used

to calculate the PM10 emission rate based on material throughput, average wind speed and material moisture

content. The throughput and number of handling steps were based on 2017 production rates and are shown in

Table 4-9. Most material handling sources at Mortimer are enclosed and a control efficiency of 90% was assumed

for all sources.

𝑬 = 𝟎. 𝟎𝟎𝟎𝟓𝟔 (𝑼

𝟐.𝟐)𝟏.𝟑 × (

𝑴

𝟐)−𝟏.𝟒 𝒌𝒈/𝒕𝒐𝒏𝒏𝒆 Equation 4-2

Table 4-9: Material Handling Throughputs

Material Throughput

(tonnes/annum)

Number of Handling

Steps Material Moisture Content

Concentrate 320 860 4 15

Coal 9 310 3 2.8

Furnace Matte 31 750 1 2.5

Crushing

Fugitive dust emissions from matte crushing were estimated using the US EPA AP42 11.24 (Metallic Minerals

Processing and 11.19.2 (Crushed Stone Processing and Pulverized Mineral Processing) single value emission

factors for primary and secondary crushing (0.02 kg/tonne and 0.0012 kg/tonne respectively). The 2017 matte

production rate (31 745 tonnes/annum) was used to calculate fugitive emissions from crushing activities.

Vehicle Exhaust

PM, SO2 and NOx emissions from vehicle exhaust were estimated using the Australian NPI Emission Estimation

Technique Manual for Combustion Engines. The emission factors for very heavy goods vehicles (vehicles with

weight > 25 tonne gross vehicle mass) are given as 1.2 kg/m³ for PM10, 0.085 kg/m3 for SO2 and 22 kg/m³ for NOx

(the units are in kg emissions per m³ of fuel consumed). The vehicle distances travelled on-site are given in Table

4-8. It was assumed that vehicles on-site consume approximately 40 l/100 km (WSP, 2017) of fuel due to higher

than average idling times.



Emission Summary

A summary of all quantified emissions from the Mortimer Smelter, as described in Sections 4.2 and 4.3 are given

in Table 4-10 and Figure 4-2 to Figure 4-4.

Table 4-10: Summary of Emissions from the Mortimer Smelter Operations

Emission Source Emission Rate (g/s)

PM10 SO2 NOx

Primary Stack 1 154 0.3

Flash Dryer 10.3 3.6 4.4

Furnace Building 0.5 0.4

Crushers 3E-04

Vehicle Exhaust 2E-04 1E-04 0.004

Vehicle Entrainment 0.11

Materials Handling 0

Wind Erosion 0.34

Emergency Incidents

No emergency incidents were reported at the Mortimer Smelter over the last two years.



Figure 4-2: Source Contributions – SO2 Emissions

Figure 4-3: Source Contributions – PM10 Emissions

Figure 4-4: Source Contributions – NOx Emissions



IMPACT OF ENTERPRISE ON THE RECEIVING ENVIRONMENT

Analysis of Emissions’ Impact on Human Health

Study Methodology

Study Plan

The study methodology may conveniently be divided into a “preparatory phase” and an “execution phase”. The

basic methodology followed in this assessment is provided in Figure 5-1.

The preparatory phase included the following basic steps prior to performing the actual dispersion modelling and

analyses:

1. Understand Scope of Work

2. Assign Appropriate Specialists (See Appendix A)

3. Review of legal requirements (e.g. dispersion modeling guidelines) (see Section 5.1.2)

4. Prepare a Plan of Study

5. Decide on Dispersion Model (see Section 5.1.1.2)

The Regulations Regarding Air Dispersion Modelling (Gazette No 37804 published 11 July 2014) was referenced

for the dispersion model selection. Three levels of assessment are defined in the Regulations regarding Air

Dispersion Modelling:

• Level 1: where worst-case air quality impacts are assessed using simpler screening models

• Level 2: for assessment of air quality impacts as part of license application or amendment processes,

where impacts are the greatest within a few kilometers downwind (less than 50 km)

• Level 3: requires more sophisticated dispersion models (and corresponding input data, resources and

model operator expertise) in situations:

- where a detailed understanding of air quality impacts, in time and space, is required;

- where it is important to account for causality effects, calms, non-linear plume trajectories, spatial

variations in turbulent mixing, multiple source types, and chemical transformations;

- when conducting permitting and/or environmental assessment process for large industrial

developments that have considerable social, economic and environmental consequences;

- when evaluating air quality management approaches involving multi-source, multi-sector

contributions from permitted and non-permitted sources in an airshed; or,

- when assessing contaminants resulting from non-linear processes (e.g. deposition, ground-level

ozone (O3), particulate formation, visibility).

The models recommended for Level 3 assessments are CALPUFF or SCIPUFF. In this study, CALPUFF was

selected on the basis that this Lagrangian Gaussian Puff model is well suited to simulate low or calm wind speed

conditions. Alternative regulatory models such as the US EPA AERMOD model treats all plumes as straight-line

trajectories, which under calm wind conditions grossly over-estimates the plume travel.



The execution phase (i.e. dispersion modelling and analyses) firstly involves gathering specific information in

relation to the emission source(s) and site(s) to be assessed. This includes:

• Source information: Emission rate, exit temperature, volume flow, exit velocity, etc.;

• Site information: Site building layout, terrain information, land use data;

• Meteorological data: Wind speed, wind direction, temperature, cloud cover, mixing height;

• Receptor information: Locations using discrete receptors and/or gridded receptors.

The model uses this specific input data to run various algorithms to estimate the dispersion of pollutants between

the source and receptor. The model output is in the form of a simulated time-averaged concentration at the

receptor. These simulated concentrations are added to measured background concentrations and compared with

the relevant ambient air quality standard or guideline. In some cases, post-processing can be carried out to produce

percentile concentrations or contour plots that can be prepared for reporting purposes.

Figure 5-1: The basic study methodology followed for the assessment



CALPUFF/CALMET Modelling Suite

As discussed in the previous section, the CALPUFF model was selected for use in the current investigation to

predict maximum short-term (1 and 24-hour) and annual average ground-level concentrations at various receptor

locations within the computational domain. CALPUFF is a multi‐layer, multi‐species non‐steady‐state puff

dispersion model that can simulate the effects of time‐ and space‐varying meteorological conditions on pollutant

transport, transformation, and removal (Scire et al., 2000). It can accommodate arbitrarily varying point source,

area source, volume source, and line source emissions. The CALPUFF code includes algorithms for near‐source

effects such as building downwash, transitional plume rise, partial plume penetration, sub grid scale terrain

interactions as well as longer range effects such as pollutant removal due to wet scavenging and dry deposition,

chemical transformation, vertical wind shear, overwater transport and coastal interaction effects. The model is

intended for use on scales from tens of metres to hundreds of kilometres from a source (US EPA 1998).

The CALPUFF model allows the user to select from a number of calculation options, including a choice of

dispersion coefficient and chemical transformation formulations. The different dispersion coefficient approaches

accommodated in the CALPUFF model include:

• stability‐based empirical relationships such as the Pasquill‐Gifford or McElroy‐Pooler dispersion

coefficients;

• turbulence‐based dispersion coefficients (based on measured standard deviations of the vertical and

crosswind horizontal components of the wind); and

• similarity theory to estimate the turbulent quantities using the micrometeorological variables calculated by

CALMET.

The most desirable approach is to use turbulence‐based dispersion coefficients using measured turbulent velocity

variances or intensity components, if such data are readily available and they are of good quality. However, since

reliable turbulent measurements are generally not available, the next best recommendation is to use the similarity

approach.

CALPUFF has the capability to model the effects of vertical wind shear by explicitly allowing different puffs to be

independently advected by their local average wind speed and direction, as well as by optionally allowing well‐

mixed puffs to split into two or more puffs when across-puff shear becomes important. Another refinement is an

option to use a probability density function (pdf) model to simulate vertical dispersion during convective conditions.

The CALPUFF modelling system consists of a number of software components, as summarised in Table 5-1,

however only CALMET and CALPUFF contain the simulation engines to calculate the three-dimensional

atmospheric boundary layer conditions and the dispersion and removal mechanisms of pollutants released into

this boundary layer. The other components are mainly used to assist with the preparation of input and output data.

Table 5-1 also includes the development versions of each of the codes used in this investigation.



Table 5-1: Summary description of CALPUFF/CALMET model suite with versions used in the investigation

Module Version Description

CALMET v6.334 Three-dimensional, diagnostic meteorological model

CALPUFF v6.42

Non-steady-state Gaussian puff dispersion model with chemical removal, wet and

dry deposition, complex terrain algorithms, building downwash, plume fumigation

and other effects.

CALPOST v5.6394 A post-processing program for the output fields of meteorological data,

concentrations and deposition fluxes.

CALSUM v1.4 (1) Sums and scales concentrations or wet/dry fluxes from two or more source groups

from different CALPUFF runs

PRTMET v 4.495(1) Lists selected meteorological data from CALMET and creates plot files

POSTUTIL v1.641(1)

Processes CALPUFF concentration and wet/dry flux files. Creates new species as

weighted combinations of modelled species; merges species from different runs

into a single output file; sums and scales results from different runs; repartitions

nitric acid/nitrate based on total available sulfate and ammonia.

TERREL v3.69(1) Combines and grids terrain data

CTGPROC v3.5(1) Processes and grids land use data

MAKEGEO v3.2(1) Merges land use and terrain data to produce the geophysical data file for CALMET

Note (1): These modules indicate version number as listed on http://www.src.com/calpuff/download/mod6_codes.htm (for CALPro Plus v6)

[version number not given in GUI interface or ‘About’ information].

Legal Requirements

Atmospheric Impact Report

According to the NEMAQA, an Air Quality Officer (AQO) may require the submission of an Atmospheric Impact

Report (AIR) in terms of section 30, if:

• The AQO reasonably suspects that a person has contravened or failed to comply with the AQA or any

conditions of an AEL and that detrimental effects on the environment occurred or there was a contribution

to the degradation in ambient air quality.

• A review of a provisional AEL or an AEL is undertaken in terms of section 45 of the AQA.

The format of the Atmospheric Impact Report is stipulated in the Regulations Prescribing the Format of the

Atmospheric Impact Report.



National Ambient Air Quality Standards

Measured and modelled concentrations were assessed against National Ambient Air Quality Standards (NAAQS

- Table 5-2) published on 24th of December 2009 (Government Gazette 32816). Sulfur dioxide (SO2), Inhalable

Particulates (PM10) and Nitrogen Dioxide (NO2) are the pollutants of concern in this assessment.

Table 5-2: National Ambient Air Quality Standards for SO2, PM10 and NO2

Pollutant Averaging Period Concentration (µg/m³) Frequency of Exceedance

Sulfur Dioxide (SO2)

10 minutes 500 526

1 hour 350 88

24 hour 125 4

1 year 50 0

PM10

24 hour 75 4

1 year 40 0

PM2.5

24 hour 40 4

1 year 20 0

Nitrogen Dioxide (NO2)

1 hour 200 88

1 year 40 0

Minimum Emission Standards

The activities at Mortimer Smelter are considered Listed Activities under Section 21 of NEM:AQA and require an

Atmospheric Emissions License (AEL) to operate (see Section 1.4). The Existing Plant and New Plant Minimum

Emission Standards (MES) for Subcategory 4.1: Drying and Calcining (applicable to the Flash Dryer) and

Subcategory 4.16: Smelting and Converting of Sulphide Ores (applicable to the Electric Furnace Stack) are given

in Table 5-3 and Table 5-4 respectively.

Current operations (Table 4-2) comply with the existing plant MES for all sources and all pollutants with the

exception of SO2 from the Main Stack, for which an interim monthly average limit of 30 000 mg/Nm³ was granted

following the 2015 postponement application. Significant reductions in SO2 will be effected once the WSA is in full

operation.

It is anticipated that, with the exception of SO2 from the Electric Furnace stack (for which this postponement

application is made), that all other pollutants from all other sources, including other pollutants from the Main Stack,

will be in compliance with the New Plant MES by 1 April 2020.



Table 5-3: Listed Activity Subcategory 4.1

Category 4.1: Drying and calcining of mineral solids including ore

Description: Drying and calcining of mineral solids including ore

Application: Facilities with capacity of more than 100 tonnes/month product

Substance or Mixture of Substances Existing Plant

emission limits:

mg/Nm³ under

normal conditions of

273K and 101.3kPa

New Plant emission

limits: mg/Nm³

under normal

conditions of 273

Kelvin and 101.3 kPa

Common

Name Chemical Symbol

Particulate Matter PM 100 50

Sulphur Dioxide SO2 1000 1000

Oxides of nitrogen NOx expressed as NO2 1200 500

Table 5-4: Listed Activity Subcategory 4.16: Smelting and Converting of Sulphide Ores

Category 4.16: Smelting and Converting of Sulphide Ores

Description: Processes in which sulphide ores are smelted, roasted, calcined or converted

Application: All installations

Substance or Mixture of Substances Existing Plant

emission limits:

mg/Nm³ under

normal conditions of

273K and 101.3kPa

New Plant emission

limits: mg/Nm³

under normal

conditions of 273

Kelvin and 101.3 kPa

Common

Name Chemical Symbol

Particulate Matter PM 100 50

Oxides of nitrogen NOx expressed as NO2 1200 500

Sulphur dioxide (feed SO2 >5% SO2) SO2 3500 1200

Dispersion Modelling Guidelines

Air dispersion modelling provides a cost-effective means for assessing the impact of air emission sources, the

major focus of which is to determine compliance with the relevant ambient air quality standards. The Regulations

Regarding Air Dispersion Modelling was published in Government Gazette No 37804 published 11 July 2014 and

recommends a suite of dispersion models to be applied for regulatory practices as well as guidance on modelling

input requirements, protocols and procedures to be followed. The guideline to air dispersion modelling is

applicable:



(a) in the development of an air quality management plan, as contemplated in Chapter 3 of NEMAQA;

(b) in the development of a priority area air quality management plan, as contemplated in Section 19 of

NEMAQA;

(c) in the development of an atmospheric impact report, as contemplated in Section 30 of NEMAQA; and,

(d) in the development of a specialist air quality impact assessment study, as contemplated in Chapter 5 of

NEMAQA.

These regulations are therefore applicable to the development of this report. The first step in the dispersion

modelling exercise requires an objective of the modelling exercise and thereby gives clear direction to the choice

of the dispersion model most suited for the purpose. Chapter 2 of the Guideline presents the typical levels of

assessments, technical summaries of the prescribed models (SCREEN3, AERSCREEN, AERMOD, SCIPUFF,

and CALPUFF) and good practice steps to be taken for modelling applications.

Dispersion modelling provides a versatile means of assessing various emission options for the management of

emissions from existing or proposed installations. Chapter 3 of the Guideline prescribes the source data input to

be used in the models. Dispersion modelling can typically be used in the:

• Apportionment of individual sources for installations with multiple sources. In this way, the individual

contribution of each source to the maximum ambient predicted concentration can be determined. This

may be extended to the study of cumulative impact assessments where modelling can be used to simulate

numerous installations and to investigate the impact of individual installations and sources on the

maximum ambient pollutant concentrations.

• Analysis of ground level concentration changes as a result of different release conditions (e.g. by

changing stack heights, diameters and operating conditions such as exit gas velocity and temperatures).

• Assessment of variable emissions as a result of process variations, start-up, shut-down or abnormal

operations.

• Specification and planning of ambient air monitoring programmes which, in addition to the location of

sensitive receptors, are often based on the prediction of air quality hotspots.

The above options can be used to determine the most cost-effective strategy for compliance with the NAAQS.

Dispersion models are particularly useful under circumstances where the maximum ambient concentration

approaches the ambient air quality limit value and provide a means for establishing the preferred combination of

mitigation measures that may be required including:

• Stack height increases;

• Reduction in pollutant emissions through the use of air pollution control systems (APCS) or process

variations;

• Switching from continuous to non-continuous process operations or from full to partial load.

Chapter 4 of the Guideline prescribes meteorological data input from on-site observations to simulated

meteorological data. The chapter also gives information on how missing data and calm conditions are to be treated

in modelling applications. Meteorology is fundamental for the dispersion of pollutants because it is the primary



factor determining the diluting effect of the atmosphere. Therefore, it is important that meteorology is carefully

considered when modelling.

New generation dispersion models, including models such as AERMOD and CALPUFF1, simulate the dispersion

process using planetary boundary layer (PBL) scaling theory. PBL depth and the dispersion of pollutants within

this layer are influenced by specific surface characteristics such as surface roughness, albedo and the availability

of surface moisture:

• Roughness length (zo) is a measure of the aerodynamic roughness of a surface and is related to the

height, shape and density of the surface as well as the wind speed.

• Albedo is a measure of the reflectivity of the Earth’s surface. This parameter provides a measure of the

amount of incident solar radiation that is absorbed by the Earth/atmosphere system. It is an important

parameter since absorbed solar radiation is one of the driving forces for local, regional, and global

atmospheric dynamics.

• The Bowen ratio provides measures of the availability of surface moisture injected into the atmosphere

and is defined as the ratio of the vertical flux of sensible heat to latent heat, where sensible heat is the

transfer of heat from the surface to the atmosphere via convection and latent heat is the transfer of heat

required to evaporate liquid water from the surface to the atmosphere.

Topography is also an important geophysical parameter. The presence of terrain can lead to significantly higher

ambient concentrations than would occur in the absence of the terrain feature. In particular, where there is a

significant relative difference in elevation between the source and off-site receptors large ground level

concentrations can result. Thus, the accurate determination of terrain elevations in air dispersion models is very

important.

The modelling domain would normally be decided on the expected zone of influence; the latter extent being defined

by the predicted ground level concentrations from initial model runs. The modelling domain must include all areas

where the ground level concentration is significant when compared to the air quality limit value (or other guideline).

Air dispersion models require a receptor grid at which ground-level concentrations can be calculated. The receptor

grid size should include the entire modelling domain to ensure that the maximum ground-level concentration is

captured and the grid resolution (distance between grid points) sufficiently small to ensure that areas of maximum

impact adequately covered. No receptors however should be located within the property line as health and safety

legislation (rather than ambient air quality standards) is applicable within the site.

Atmospheric Dispersion Processes

CALPUFF initiates the simulation of point source plumes with a calculation of buoyant plume rise as discussed

below in Section 5.1.3.1. Transport winds are extracted from the meteorological data file at the location of the

stack and at the effective plume height (stack height plus plume rise). For near-field effects, the height of the

1 The CALMET modelling system require further geophysical parameters including surface heat flux, anthropogenic heat flux and leaf area

index (LAI).



plume in transition to the final plume height is taken into account. The puff release rate is calculated internally,

based on the transport speed and the distance to the closest receptor.

As the puff is transported downwind, it grows due to dispersion and wind shear, and the trajectory is determined

by advection winds at the puff location and height at each time step. The pollutant mass within each puff is initially

a function of the emission rate from the original source. The pollutant mass is also subject to chemical

transformation, washout by rain and dry deposition, when these options are selected. Chemical transformation

and removal are calculated based on a one-hour time step.

Both wet and dry deposition fluxes are calculated by CALPUFF, based on a full resistance model for dry deposition

and the use of precipitation rate-dependent scavenging coefficients for wet deposition. Pollutant mass is removed

from the puff due to deposition at each time step. For the present modelling analyses, most options were set at

“default” values, including the treatment of terrain.

Plume Buoyancy

Gases leaving a stack mix with ambient air and undergo three phases namely the initial phase, the transition phase

and the diffusion phase (Figure 5-2). The initial phase is greatly determined by the physical properties of the

emitted gases. These gases may have momentum as they enter the atmosphere and are often heated and

therefore warmer than the ambient air. Warmer gases are less dense than the ambient air and are therefore

buoyant. A combination of the gases' momentum and buoyancy causes the gases to rise (vertical jet section, in

Figure 5-2). In the Bent-Over Jet Section, entrainment of the cross flow is rapid because, by this time, appreciable

growth of vortices has taken place. The self-generated turbulence causes mixing and determines the growth of

plume in the thermal section. This is referred to as plume rise and allows air pollutants emitted in this gas stream

to be lofted higher in the atmosphere. Since the plume is higher in the atmosphere and at a further distance from

the ground, the plume will disperse more before it reaches ground level. With greater volumetric flow and increased

exit gas temperatures, the plume centreline would be higher than if either the volumetric flow or the exit gas

temperature is reduced. The subsequent ground level concentrations would therefore be lower.

This is particularly important in understanding some of the dispersion model results in Section 5.1.7. As an

example, consider the emissions from the Furnace Main Stack. With the introduction of retrofitted emission

controls (such as the WSA Plant) the volumetric flow would be lower than the original values. In this case the exit

temperature increases while the exit velocity is increased. It is therefore possible that the change in plume

momentum and buoyancy may result in higher or lower ground level concentrations due to the lower or higher

plume centreline.



Figure 5-2: Plume buoyancy

Urban & Rural Conditions

Land use information is important to air dispersion modelling, firstly to ensure that the appropriate dispersion

coefficients and wind profiles (specified as surface roughness) are used, and secondly, that the most appropriate

chemical transformation models are employed. Urban conditions result in different dispersion conditions than in

rural areas, as well as changing the vertical wind profiles. Urban conditions are also generally associated with

increased levels of volatile organic compounds (VOCs), thereby influencing chemical equilibriums between the

photochemical reactions of NOx, CO and O3.

It can be appreciated that the definition of urban and rural conditions for the dispersion coefficients and wind

profiles, on the one hand, and chemical reactions on the other, may not be the same. Nonetheless, it was decided

to use the US Environmental protection Agency’s (US EPAs) guideline on air dispersion models (US EPA 2005),

to classify the surrounding land-use as rural or urban based on the Auer method, which is strictly recommended

for selecting dispersion coefficients.

The classification scheme is based on the activities within a 3 km radius of the emitting stack. Areas typically

defined as rural include residences with grass lawns and trees, large estates, metropolitan parks and golf courses,

agricultural areas, undeveloped land and water surfaces. An area is defined as urban if it has less than 35%

vegetation coverage or the area falls into one of the use types in Table 5-5.



Table 5-5: Definition of vegetation cover for different developments (US EPA 2005)

Urban Land-Use

Type Development Type Vegetation Cover

I1 Heavy industrial Less than 5%

I2 Light/moderate industrial Less than 10%

C1 Commercial Less than 15%

R2 Dense/multi-family Less than 30%

R3 Multi-family, two storeys Less than 35%

According to this classification scheme the surroundings at Mortimer Smelter are classified as rural.

Model Input

Meteorological Input Data

The option of Partial Observations was selected for the CALMET wind field model which used both measured and

observed meteorological data. Mortimer Smelter operates four on-site meteorological stations co-located with the

ambient monitoring stations (Figure 1-1). Hourly average wind speed, wind direction and temperature data from

these stations were available for the period January to December 2017.

The Weather Research and Forecasting (WRF) Model data provided the parameters useful for describing the

dispersion and dilution potential of the site i.e. wind speed, wind direction, temperature and atmospheric stability,

as discussed below. The WRF Model is a next-generation mesoscale numerical weather prediction system

designed for both atmospheric research and operational forecasting needs. It features two dynamical cores, a data

assimilation system, and a software architecture facilitating parallel computation and system extensibility. The

model serves a wide range of meteorological applications across scales from tens of meters to thousands of

kilometres. The Regulations Regarding Dispersion Modelling recommend the use of WRF data as it is the current

operational model at the South African Weather Service (SAWS). WRF data for the period 2014 to 2016 on a

12 km horizontal resolution for a 50 km by 50 km was used.

Land Use and Topographical Data

Readily available terrain and land cover data for use in CALMET was obtained from the Atmospheric Studies Group

(ASG) via the United States Geological Survey (USGS) web site at ASG. Use was made of Shuttle Radar

Topography Mission (SRTM) (90 m, 3 arc-sec) data and Lambert Azimuthal land use data for Africa.

Grid Resolution and Model Domain

The CALMET modelling domain included an area of 50 km by 50 km with a grid resolution of 1 km. The CALPUFF

model domain selected for the sources at Mortimer Smelter and the location of nearby sensitive receptor locations

extended over a modelling domain of 15 km by 15 km with a grid resolution of 100 m over the entire modelling

domain.



Atmospheric Dispersion Potential

Meteorological mechanisms govern the dispersion, transformation, and eventual removal of pollutants from the

atmosphere. The analysis of hourly average meteorological data is necessary to facilitate a comprehensive

understanding of the dispersion potential of the site. The horizontal dispersion of pollution is largely a function of

the wind field. The wind speed determines both the distance of downward transport and the rate of dilution of

pollutants.

For this assessment, on-site measured meteorological data together with The Weather Research and Forecasting

(WRF) Model data provided the parameters useful for describing the dispersion and dilution potential of the site

i.e. wind speed, wind direction, temperature and atmospheric stability, as discussed below. Measured on-site data

was available for the period January 2017 to December 2017, while WRF data was obtained for January 2014 to

December 2016.

The WRF data was obtained from Lakes Environmental (Canada), and was prepared for a modelling domain of 50

km (East-West) by 50 km (North-South). The meteorological information was supplied on a horizontal grid spacing

of 12 km.

Surface Wind Field

Wind roses comprise 16 spokes, which represent the directions from which winds blew during a specific period.

The colours used in the wind roses below, reflect the different categories of wind speeds; the red area, for example,

representing winds >11.1 m/s. The dotted circles provide information regarding the frequency of occurrence of

wind speed and direction categories. The frequency with which calms occurred, i.e. periods during which the wind

speed was below 0.5 m/s are also indicated.

The period wind field, diurnal and seasonal variability for the study area (based on the CALMET processed WRF

and on-site meteorological data) are provided in Figure 5-3 and Figure 5-4. The average wind speed for the period

2014 to 2016 was 2.7 m/s. The predominant wind directions are from the north and northwest during the day and

from the east and southeast at night. Seasonal variability shows that winds from the northern sector are more

prevalent during spring and summer while winds from the southern sector are more prevalent during autumn and

winter.



Figure 5-3: Period, day- and night-time wind rose for the period 2014 – 2016 (CALMET Processed WRF and

On-site Data).

Figure 5-4: Seasonal wind roses for the period 2014 – 2016 (CALMET Processed WRF and On-site Data).



Temperature

Air temperature is important, both for determining the effect of plume buoyancy (the larger the temperature

difference between the emission plume and the ambient air, the higher the plume is able to rise), and determining

the development of the mixing and inversion layers.

Average temperatures in the study area between 2014 and 2017 ranged between -0.1°C (recorded in July) and

41.0°C (recorded in January). During the day, temperatures increase to reach maximum at around 17:00 in the

afternoon. Ambient air temperature decreases to reach a minimum at around 06:00 i.e. near sunrise.

Figure 5-5: Monthly average temperature (°C) profile for the period 2014 to 2016



Air Quality Monitoring data

Ambient concentrations of SO2 and PM10 are monitored by AAP at four locations in the vicinity of Mortimer Smelter

as shown in Figure 1-1. Ambient monitoring results in comparison to the SA NAAQS are shown in Figure 5-7,

Figure 5-8 and Figure 5-9 for annual, daily and hourly SO2 and Figure 5-10 and Figure 5-11 for annual and daily

PM10. A summary of monitoring results is shown in Table 5-6. Background SO2 and PM10 concentrations were

estimated by calculating the median (50th percentile) concentration over the four-year monitoring period.

During 2017, sampled hourly, daily and annual average SO2 concentrations were in compliance with the

SA NAAQS at all four sampling locations. Ground level SO2 concentrations are expected to improve

significantly once the WSA Plant is operational.

Daily average PM10 concentrations recorded at the Bierspruit station (which is located the furthest from Mortimer

Smelter - Figure 1-1) exceeded the SA NAAQS limit value of 75 µg/m³ on five days during 2017. The NAAQS

allow for four exceedances of the limit value per calendar year. Recorded annual average and highest daily PM10

concentrations at all other monitoring stations were in compliance with the SA NAAQS during 2017.

Figure 5-6: Background (median) concentrations recorded at the four APP monitoring stations during 2017



Table 5-6: Summary of 2014 to 2017 Ambient Monitoring Results

Averaging Period SA

NAAQS 4B

Decline Bierspruit

Fridge Plant

Mortimer

SO2

Data Availability 91.4% 78.2% 68.0% 74.3%

Annual Average 50 µg/m³ 15.1 3.8 8.5 18.9

Highest Daily 125 µg/m³ 62.6 27.3 42.9 105.9

Daily frequency of exceedance of NAAQS Limit Value 4 days 0 0 0 0

Highest Hourly 350 µg/m³ 595.3 183.7 364.8 680.2

Hourly frequency of exceedance of NAAQS Limit Value 88 hours 6 0 1 21

PM10

Data Availability 99.7% 95.6% 64.7% 47.4%

Annual Average 40 µg/m³ 23.0 20.3 23.2 23.6

Highest Daily 75 µg/m³ 68.6 108.1 77.2 64.8

Daily frequency of exceedance of NAAQS Limit Value 4 days 0 5 1 0

Figure 5-7: Annual average SO2 concentration recorded at the four AAP monitoring stations during 2017.



Figure 5-8: 99th Percentile daily SO2 concentrations at the four AAP monitoring stations (no exceedances

of the NAAQS limit value of 125 µg/m³ for SO2 were recorded during 2017)

Figure 5-9: Hourly exceedances of the NAAQS limit value for SO2 recorded at the four AAP monitoring

stations during 2017.



Figure 5-10: Annual average PM10 concentration recorded at the four AAP monitoring stations during 2017

Figure 5-11: Daily exceedances of the NAAQS limit value for PM10 recorded at the four AAP monitoring

stations during 2017.

Atmospheric Impact R

Documents

ATMOSPHERIC IMPACT REPORT: MORTIMER SMELTER...Platinum District Municipality in the North West Province. RPM holds an Atmospheric Emissions Licence (AEL) for its operations and is