5 Tonkin & Taylor Ltd Waihi North Project - Technical Review of Air Quality Assessments Oceana Gold (New Zealand) Limited 22 June 2022 Job No: 1017908.0000 Sections 7.4 details the overall assessment of potential dust effects for the Gladstone Open Pit (GOP), the Tailings Storage Facility (TSF3) and the North Rock Stack (NRS). Overall, we consider the detail for this section would benefit from a more structured consideration of the FIDOL factors or the approach set out by the IAQM. Notwithstanding this, the following summarises our consideration of each of the above dust sources: • GOP: The nearest residential dwelling is approximately 310 m from the pit and is located downwind during prevailing winds and very infrequently downwind during strong wind conditions. Other sensitive residential locations are located further afield and similarly not downwind during prevailing or strong wind conditions. Overall, we agree with the conclusions reached by Beca in relation to the GOP, on the basis that the wind exposure and separation distances for the nearest sensitive locations are such that the frequency, intensity and duration of impacts are likely to be low. Further mitigating the potential effects is that the potential sources of dust associated with the GOP will increasingly be below ground level and the pit is excavated and deepens. • TSF3: One existing rural residence is located approximately 250 m from the TSF3. Beca identifies that a further dwelling could be established approximately 180 from the TSF3. These are moderately close distances which will provide for a reasonable reduction in dust and fine particulate matter. Furthermore, neither of these receptor locations are downwind during prevailing or frequent strong wind conditions, which will significantly reduce the potential frequency and duration of exposure to dust from mining activities. However, given the elevated nature of the TSF3 and its stockpiles relative to the surrounding environment and the moderately close proximity of the two receptors to the TSF3 and stockpiles, the use of continuous dust monitoring and proactive mitigation in response to dust trigger events is recommended to provide surety that dust levels are suitably managed. • NRS: Sensitive receptors located are approximately 90 and 100 m to the east of the closest stockpile associated with the NRS, and approximately 300 to 450 m from the NRS itself. The sensitive receptors are downwind of the NRS during prevailing and strong wind conditions. In this instance the key concern is the separation distance to the stockpiles, while the separation to the NRS is comparatively large which should provide sufficient distance such that dust levels are comparatively low. The Beca report notes that additional mitigation is likely to be required to address potential dust effects during the construction of the stockpiles, which we agree with in principle. However, we also consider that continuous dust monitoring as discussed above will be needed to help manage potential dust events as they arise. Section 7.5 discusses effects of fine particulates, respirable silica, combustion emissions and blast emissions. In this regard, comparison is made to monitoring PM10, PM2.5 and RCS concentrations that has been carried out in the vicinity of the Martha Pit, which we agree is reasonable and likely to be representative (albeit conservative given the rural location of the WNP). Overall, we agree with the conclusions reached by Beca relating to PM10, PM2.5 and RCS emissions. Section 7.6 discusses the potential effects on vegetation, and we agree with the conclusions reached by Beca that those effects are expected to be low. Section 7.7 considers the potential effects of the Processing Plant. Consideration of the metal discharges (including mercury) are summarised in the Waihi Facilities Report, which is the subject of the Processing Plant Report that we discuss later in Section 3 of this document. However, the Waihi Facilities Report addresses particulate discharges associated with the Processing Plant. In this regard it refers to Victoria EPA separation distance guidelines6, which recommends a separation distance of 250 m from between the source of dust and sensitive location. In our experience, a much larger 6 Vic EPA 2013. Recommended separation distances for industrial residual air emissions. Environmental Protection Authority Victoria. Publication number 15180
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