Sources of SO2

2 oven stacks (BO1 & BO2) – constant emissions average emission rate Fugitive emissions from bake oven buildings – several volume sources with hourly emissions file with constant emissions and modelled 10°C above ambient 7 Gas treatment stacks – constant emissions average emission rate

Overview

A review of the monitoring data found:

• 21 exceedances of 24-hr SO2 at School Drive

• 9 exceedances of 24-hr SO2 at the Farm

• No exceedances of 1-hr SO2 standard at any site during these periods

• Exceedances occurred during extended periods of strong westerly winds (prevalent in winter months)

• Previous air dispersion modelling of the site did not highlight these meteorological conditions as a potential issue

• Measured SO2 concentrations at the Highway, Laverick Avenue and at the Met station comply with 1-hr and 24-hr SO2 NEPM standard of 570 µg/m3 and 228 µg/m3, respectively

A CASE STUDY: TOMAGO ALUMINIUM SMELTER

Further information Katestone has been a leading provider of expert

air quality and meteorology services since 1989.

It now assists clients with sustainability, climate

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team of 20 professionals have established an

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P (07) 3369

3699

Donnelly, Sarah-Jane1, Shaw, Natalie2, Killip, Christine3, Roser, Neil4

1 Senior Consultant, Katestone Environmental, Brisbane 2 Principal Consultant, Katestone Environmental, Brisbane 3 Managing Director, Katestone Environmental, Brisbane 4Environment Services Team Leader, Tomago Aluminium Company, Newcastle

Dispersion modelling

Objective: Determine the source of 24-hour exceedances of SO2

TAC ambient monitoring for SO2 consists of five sites within 1.1 km of the site, with monitoring

Analysis of measured data

30 May 2 Aug 12 Aug 16 Aug 24 Aug 26 Aug 27 Aug 16 Sep 22 Jun 9 Jul 11 Jul 12 Jul

Carbon Bake Fugitive 59.9 42.8 46.4 61.8 65.6 37.4 56.9 45.1 39.0 44.9 62.5 40.4

Gas Treatment Stacks 13.2 20.4 18.4 19.9 20.9 23.0 19.3 26.3 7.8 11.8 12.3 19.9

Bake Oven Stacks 51.1 51.3 51.2 68.3 75.3 35.4 64.6 46.0 54.6 63.3 77.9 69.6

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Modelled source contribution of 24-hour average SO2 at the School monitoring station

The analysis of monitoring data suggests:

• A wake effected stack source

•Direction of source consistent with bake ovens

Wind tunnel modelling

Emissions

Sources of SO2

2 Bake oven stacks (BO1 & BO2) – constant emissions average emission rate Fugitive emissions from bake oven buildings – several volume sources with hourly emissions file with constant emissions and modelled 10°C above ambient 7 Gas treatment stacks – constant emissions average emission rate

Risk Assessment

Modelled met file Building wakes Source configuration Stack tip downwash Shut down of bake ovens

Met file representative of site Important to local dispersion Roof vents modelled as several volume sources May be important Residual emissions occur

1- Hazard identification Recognise that there are exceedances and therefore a hazard

4- Risk characterisation The risk assessment was expressed as a hazard index for each sulphur dioxide air quality criteria and averaging period The hazard index was calculated as follows: Where: HI is the hazard index Max Ci is the maximum concentration measured (or predicted by dispersion model) in a zone for a particular pollutant averaging period i AQCi is the air quality criteria for the pollutant Max Ci for averaging period i

Conclusions: TAC should consider options for mitigating potential impacts at residences within 1 km to the east of the smelter. TAC should consider undertaking further investigation of sulfur dioxide levels at the Detention Centre.

2- Assessment of exposure Identification of sensitive receptor locations

3- Dose response assessment Evaluate the qualitative and quantitative toxicity information to estimate the incidence of adverse effects occurring in humans at different exposure levels

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School Drive Farm

Contour of scaled up predicted maximum 24-hour average SO2 ground-level concentrations to match measurements. Shows the area of potential exceedance or the areas ‘at risk’

Results showed a number of receptors in zone 1 were at risk

Sources of SO2

•2 Bake oven stacks (BO1 & BO2) •Fugitive emissions from bake oven buildings •7 Gas treatment stacks

Fugitive emissions: Investigated side and roof vents Side vents not a source of emissions during event days

Emissions measurement: BO1, roof vents and gas treatment stacks

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SO2 concentration (mg/m3) Emission rate (g/s)

Bake oven 1 emissions variability

Side vents on bake oven building

Sarah-Jane Donnelly

Outcome: •Main source is the gas treatment stacks (290° to 310°) •Bake oven stacks resulted in lowest concentrations •Fugitive sources impact at wind speeds of < 5 m/s

Outcome: •Modelling replicated the

general trend but concentrations were

underestimated •Major sources were the bake

oven stacks and roof vents

Investigated: Outcome:

Five SO2 monitors and met station

School Drive

The Farm

Evaluation of hazard index