1 Tonkin & Taylor Ltd Assessment of mine vent air quality impacts to inform an assessment of ecological effects on Archey’s frog Oceana Gold (NZ) Limited June 2022 Job No: 1017908 1 Introduction Oceana Gold (NZ) Limited (OGNZL) is seeking resource consents for its Waihi North Project (WNP) which includes a new underground mine, the ‘Wharekirauponga Underground Mine’ (WUG) that is located approximately 11km north-west of the current Processing Plant under land administered by the Department of Conservation (DOC) (Coromandel Forest Park). The Site infrastructure supporting the WUG will be located on OGNZL owned farmland located at the end of Willows Road, with only minimal surface features within the forest, in the form of fenced vent raises, on a legal road reserve owned by the Hauraki District Council. A number of vent raises will exhaust the ventilation air from within the mine. The vent discharges will include particulate matter and products of combustion (notably oxides of nitrogen). The general area of the proposed vent raises (vents) includes habitat for a rare frog species (Archey’s frog). This report seeks to characterise the likely air quality in and around the mine vents and provide supporting information to enable an assessment of the ecological impacts on the Archey’s frog habitat to be undertaken. The general approach used in this assessment is as follows: • Determine likely ambient air quality impacts in the vicinity of the proposed vents (through dispersion modelling). • Compare the model predictions with likely air quality adjacent to an unpaved public road in the Coromandel (north of the WUG) where a baseline ecological assessment of Archey’s frog habitat has been undertaken. The remainder of this report characterises the nature of discharges to air (Section 2), provides details of the assessment approach (Section 3), presents the dispersion modelling results that characterise the likely air quality in the vicinity of the proposed mine vents (Section 4) and compares those results to estimated concentrations adjacent to an unpaved road in the Coromandel where a population of Archey’s frog is known to occur (Section 5). This report has been prepared by Tonkin & Taylor Limited (T+T) for OGNZL in accordance with our letter of engagement dated 16 June 2021. 2 Nature of discharges to air from the vents The main discharges to air from the vents will be particulate matter and products of combustion, particularly oxides of nitrogen (NOx), from the exhausts of mining equipment and trucks, as well as from blasting events. WaterCare Services Limited (WaterCare) carried out source emission testing of total suspended particulate (TSP) and oxides of nitrogen (NOX) on an existing mine ventilation shaft vent on 15 and 16 August 2007.1 The results are summarised in Table 2.1. 1 WaterCare 2009. Newmont Waihi Gold. Particulate, Carbon Monoxide and Oxides of Nitrogen Emission Testing – August 2007 – Amended. Report prepared by WaterCare Services Limited for Newmont Waihi Gold. 10 September 2009.
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