12 Tonkin & Taylor Ltd Waihi North Project - Technical Review of Air Quality Assessments Oceana Gold (New Zealand) Limited 22 June 2022 Job No: 1017908.0000 Section 6.2 presents the model results for the range of other metal contaminants. In all cases the predicted concentrations are less than 1% of the corresponding guideline. 4.5 Section 7: Summary and recommendations Section 7 of the Processing plant report summaries the results of the modelling assessment and provides recommendations. Overall, we agree with the conclusions reached by Beca regarding the results of the dispersion modelling assessment. We note that the Waihi Facilities report describes that Oceana Gold will install the retort to control mercury emissions prior to the processing of GOP and WUG ore. We support this requirement, which will further minimise mercury emissions and should ensure low off-site concentrations relative to the assessment criteria. Section 7.2 recommends that an ongoing emission testing programme for mercury and other metals be carried out on each stack on an annual basis. This is consistent with our earlier recommendation. However, given limited information we suggest that testing should initially be carried out twice a year for an initial period of 5 years, after which time the testing could be reduced to once per year. We additionally recommend that an emission rate limit regarding mercury is included in the air discharge permit conditions to reflect the assumptions made in the Beca assessment.
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