12 Tonkin & Taylor Ltd Wharekirauponga Underground Mine – unplanned detonation air quality assessment Oceana Gold (New Zealand) Limited June 2022 Job No: 1015212.2000 vRev0 Contaminant Averaging period Concentration (µg/m3) Reference NO2 1-hour 200 NESAQ / NZ AAQG NH3 1-hour 21,000 US EPA AEGL NESAQ = National Environmental Standards for Air Quality NZ AAQG = New Zealand Ambient Air Quality Guidelines USEPA AEGL = United States Environmental Protection Agency Acute Exposure Guideline Levels There is no specific guidance in New Zealand for evaluating the significance of modelled concentrations relative to the assessment criteria. To provide context for the model results, we have adopted the framework described in UK Institute of Air Quality Management (IAQM) guidance7, as illustrated inFigure 5.1Error! Reference source not found.. Figure 5.1: Impact descriptors for individual receptors (IAQM) 5.4 Model results The predicted model results are illustrated as contour plots in Appendix D. The contour plots show that the highest GLCs are localised to approximately 130 m northeast of the vent stack in the forest reserve. A secondary concentrated area is approximately 860 m to the southeast of the vent. The contours show concentrations that are significantly influenced by impingement of the vent plumes against elevated terrain surrounding the vents. However, predicted concentrations are comparatively low. The results are discussed in terms of the effect on human health in Section 6. 7 Institute of Air Quality Management. 2017. Land-Use Planning & Development Control: Planning for Air Quality. London.
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