10 OGNZ WUG mine: assessment of potential ecological effects Project 2034 Activity Potential adverse effect (unmanaged) Avoidance/ Mitigation proposed Magnitude of effect after management (Table 8 EIANZ) Level of effect (Table 10 EIANZ) Vent shaft - discharge of air pollutants Dust, silica and diesel pollutants emitting from the stacks (as use of electric vehicles is not guaranteed). Discharges are assumed for the life of the mine (9 years). Discharge particle composition and dispersal radius is based on modelling by Richard Chilton (T+T emissions expert; T+T, 20219). The key discharges to air from the proposed vents are fine particulate matter less than ten microns (PM10) and nitrogen dioxide (NO2). Predicted cumulative ambient air concentrations of PM10 and NO2 in the vicinity of the proposed vents are very lowwhen compared against human health assessment criteria. PM10 concentrations are likely to be similar in areas adjacent to an unpaved public road in the Coromandel (north of the WUG) where baseline ecological assessments of Archey’s frog habitat have been undertaken. Therefore, it can be inferred that Archey’s frogs at roadside Coromandel locations are exposed to greater levels of PM10 than anticipated in the vicinity of the proposed vents. There are likely to be many frogs near to the proposed 4 x vent stacks. Frogs are very vulnerable to absorbing emissions in the air through their skin. The emissions will be vented 24 hours/ day – i.e. at night when frogs are active on the ground. The implications of long-term exposure to emissions at an unknown level from the vent stacks is unknown but a precautionary approach would suggest that it is not nil. A higher level of exposure to these discharges occurs within roadside areas where Archey’s frogs have been recorded and are known to persist in the Coromandel. No filters or scrubbers are proposed in the vent stacks. Mitigations proposed that are relevant to this part of the WUG site are: 1. Dampen exposed underground surfaces. Negligible Very Low Vent shafts – discharge of warm air Higher temperatures around vent shafts potentially attract frogs, their prey and introduced predators, leading to increased rates of frog predation and localised population decline. Temperature of emissions is not likely to be significantly different to ambient and will disperse quickly in air when discharged at 11m elevation. The OGNZL vent shaft design stands up to 8 m tall and emits from the top. An Animex exclusion fence will exclude animals from close proximity to vent shaft raises. Negligible Very Low 9 Tonkin & Taylor Ltd. November 2021. Assessment of mine vent air quality impacts to inform an assessment of ecological effects on Archey’s frog. Report prepared for OGNZL.
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