13 OGNZ WKP mine: assessment of potential ecological effects Project 2034 4. Management of potential residual adverse effects The assessment provided inTable 2 indicates that, under a worst-case scenario, that there could be residual adverse effects after avoidance and mitigation have been applied. There are three potential residual adverse effects that we have identified which may result in direct or indirect impacts on Archey’s or Hochstetter’s frogs within the Wharekirauponga project area. These exclude potential adverse effects that OGNZL assumes will be addressed by current consents or Authorities held by OGNZL, or those that will be obtained prior to the WNP project as part of preliminary, preparatory or prior works (Table 1). The potential effects are listed inTable 3 with a likelihood of occurrence and an estimate of the spatial area of Archey’s frog habitat and number of frogs that could be potentially affected. In this analysis we have treated pest control within the WUG surface area as mitigation, but have separated it from the potential effects of vibration, vent shaft air emission discharges and cumulative potential loss of frogs from mitigation failure. The potential benefits of pest control as mitigation or offset (depending on where the pest control is applied) is provided in the next section of this report. Table 3. Likelihood of occurrence and potential effects on frogs and frog habitat of potential adverse effects that may be associated with the WUG project. Estimates of loss of Archey’s frog habitat and loss of Archey’s frogs are based on estimates provided by Dr Lloyd. Estimates of loss are independent between rows (i.e. not cumulative). Estimates for Hochstetter’s frogs are not provided. Potential effect Likelihood of occurrence of the effect Potential loss of frog habitat Potential loss of frogs if low likelihood assessment is incorrect Vibration (episodic) – vibration at ground level at rates leading to loss of breeding success/ frog movement away Low – based on information from Golden Cross mine on Hochstetter’s frogs, vibration measurements for Archey’s frogs along Coromandel roadsides, and research by Mr van Winkel (Bioresearches). Nil Some number less than the estimated population within the potential effects footprint (estimated at around 290,000 Archey’s frogs). Vent shaft - discharge of air pollutants, leading to localised pollutant effects on frogs Very low – based on information from Archey’s frogs adjacent to Coromandel roads and research report by Mr Hilton (T+T) Nil Several thousands of frogsmay be in the vicinity of vent stacks and exposed to elevated levels of air emissions compared to the current background state (although less than levels that roadside Archey’s frogs are currently exposed to). Failure of proposed mitigation measures leading to loss of any frogs within WUG above ground footprint – resulting in increased risk of extinction or lowered population viability of the local Coromandel population Very low – as maximum vibration surface expression will be set by consent requirements, and other technical applications (frogproof mesh exclosure, dampening mine face workings, survey to ensure vent stack locations have no frogs) are proven. Low (less than 1 ha; which constitutes far less than 0.3 % of the local WUG area occupied by Archey’s frogs, and far less than 1 % of known occupied habitat by Archey’s frogs on the Coromandel Peninsula Some number less than the estimated population within the potential effects footprint (estimated at around 290,000 Archey’s frogs). The potential residual adverse effects inTable 3 all have an assessed likelihood of potentially causing adverse effects on frogs of Low or Very Low.
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