| Dispersion Model Predictions | WNP Processing Plant Air Discharge Assessment | 4397169-66885702-113 | 16/06/2022 | 20 Sensitivity: General 6 Dispersion Model Predictions 6.1 Predicted Annual Average Mercury Concentrations A summary of the annual average mercury concentrations predicted at nearby sensitive residential receptors is shown in Table 6-1 for the modelled emission scenarios. The location of the receptor points is shown in Figure 5-2. It is at these locations that people could potentially be exposed to emissions from the plant over an extended period. The predicted concentration contour plots for each of the modelled emission scenarios is shown in Appendix C. The results of the modelling indicate that emissions from the Processing Plant would not exceed any of the relevant annual average mercury concentration limits at nearby sensitive receptors for any of the modelled emission scenarios. The maximum mercury concentration predicted at any receptors for Scenarios 1and 2 are respectively 70%, and 24.7% of the OEHHA annual average guideline concentration of 0.03 µg/m3. Table 6-1. Summary of predicted annual average mercury concentrations (µg/m3) for the modelled emission scenarios Receptor Scenario 1* (existing) (µg/m3) Scenario 2 (proposed) (µg/m3) 1 0.0196 0.0068 2 0.0210 0.0074 3 0.0182 0.0067 4 0.0141 0.0044 5 0.0104 0.0032 6 0.0115 0.0033 7 0.0118 0.0041 8 0.0103 0.0041 9 0.0142 0.0043 10 0.0098 0.0029 11 0.0073 0.0024 12 0.0084 0.0028 13 0.0092 0.0033 Assessment Criteria 0.33 µg/m3 - NZAAQG 0.3 µg/m3 - USEPA RfC 0.2 µg/m3 - ATSDR MRL 0.03 µg/m3 - OEHHA REL *Scenario 1 is theoretical as the retort oven will be installed before GOP and WUG ore is processed It should be noted that predicted annual average mercury concentration at the most impacted dwelling for existing operating conditions (Scenario 1), when processing only MUG ore at 2.25 MTPA, is 0.000016 µg/m3, or 0.05% of the OEHHA guideline. 6.2 Predicted Concentrations for Other Metals A summary of maximum concentrations of non-mercury metals at the nearby dwellings most impacted by plant emissions is shown in Table 6-2. The results show that the discharges from the Processing Plant are
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