B-3 – Area 3 - Assessment of Environmental Effects 27 With respect to impacts on individual groundwater users, experience with tunnelling in Waihi as well as the groundwater modelling undertaken by GWS indicates that the lateral effects of depressurisation around the tunnel will be limited. This is due to the low rockmass permeability of andesite rock. For this reason, the assessment concludes that it is unlikely that groundwater users will be adversely affected by the tunnel development. GWS (2022a) also consider taking groundwater from the deep aquifers is not expected to affect water levels in the overlying aquifers and therefore, the potential for effects will be less than minor. Notwithstanding no effects being expected, OGNZL proposes to provide further comfort by proposing the following condition be included on its consent: If, in the opinion of the Waikato Regional Council, the exercise of this consent adversely affects any existing stock, domestic or other water supplies, then the Consent Holder shall, at its own cost, be responsible for providing to the owner of those water supplies an alternative equivalent water supply, to the satisfaction of Waikato Regional Council. The Consent Holder shall be responsible for making an alternative water supply available within 12 hours of being directed to do so by the Waikato Regional Council. 5.4.3 Monitoring GWS (2022a) recommends groundwater monitoring at two locations along the Wharekirauponga Access Tunnel alignment. The first is around the decline from the Waihi SFA where the near surface connection exists. Existing monitoring indicates that shallow groundwater system is already dewatered locally, and conditions will not change significantly as a result of the tunnel construction. GWS (2022a) recommends monitoring of groundwater using the existing network of wells in this area to ensure that no significant changes arise. There are also some groundwater bores within proximity to the Wharekirauponga Access Tunnel alignment and these bores take groundwater from a similar depth to the Wharekirauponga Access Tunnel. While it is unlikely these will be affected by the proposed tunnel, GWS (2022a) also recommends that groundwater levels in the area be monitored as the tunnel is being driven. 5.4.4 Overall Conclusion GWS (2022a) concludes that any effects on groundwater will be located to around the tunnel, and they will not manifest in any surface expression, due to the relative depth of the Wharekirauponga Access Tunnel development. The geology is similar to that at Waihi and the proposed mitigating tunnelling methodology will ensure any potential effects on groundwater and surface water are managed through existing proven techniques.
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