11 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) Dewatering of mine workings Dewatering or drying out of regolith and soils such that roots systems of old-growth forest are stressed and lead to wholesale forest decline, habitat loss and frog mortality, potentially over ca. 100 ha. The risk to soil regolith and therefore trees and vegetation from dewatering is shown in the GWS Ltd and FloSolutions reports. This risk will be avoided through the management measures detailed by Valenza Engineering such that the activity does not cause any measurable dewatering of the soil regolith or a surface water body identified as a Natural StateWater Body in the Waikato Regional Plan at the date of issue of this consent, which could have an adverse effect on vegetation or streams. We note that the resource consent conditions do not allow the mine to progress if there is a risk of measurable changes to the hydrology at the surface, except for those changes caused by changes in the flow of the warm spring located at map reference [TBC]. Grout major water ingress points into mine (if this occurs) - however note that modelling of geology and hydrology indicates limited connection between mine-depth hydrology and surface water/ subsurface groundwater, and only possibly at streams. Potential effects are therefore limited to habitat used by Hochstetter’s frogs. Nil – this effect is not feasibly possible Nil Failure of proposed mitigation measures described above and the risk of habitat or frog effects as described in the Level of Effect for each individual activity listed above, in aggregate. Reduction of frog habitat or frog population as a result of all of the other potential adverse effects, under the assumption that the above listed mitigations fail, and assuming a pre-cautionary approach to assigning likelihood of potential effect. Overall, if this were to occur, most effects would be small-scale, shortduration and very localised. The potential effect of vibration at surface could have the broadest level of adverse effect, however, that is unlikely to have a direct mortality effect on frogs, but rather potential indirect effects on breeding success, movement and predation vulnerability (if any) This is a contextual analysis. If the above mitigations fail, what will be the potential adverse effect on the persistence of Archey’s frog on the Coromandel? Archey’s frog population estimates for the Coromandel Peninsula are around 43 – 67 million individuals with frog habitat estimated to cover 578 km2. This estimate excludes lower-altitude areas (where frogs are known to occur) and excludes a 314 km2 block in central Coromandel Peninsula where there is apparent frog habitat but no survey records to confirm presence. Under the conservative estimates above, the potential vibration area for WUG includes an estimated 0.53 % - to 0.58 % of the Coromandel Peninsula Archey’s frog population and 0.54 % of the total frog habitat available in the 578 km2 block of habitat with Archey’s frog records within the Low Very Low
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