B-3 – Area 3 - Assessment of Environmental Effects 26 Hydrological control - Placement of low permeability layers, evapotranspiration layers and spoil management structures to control the potential leaching rate from the disposal facility. Rock material extracted from the development of the Wharekirauponga Access Tunnel will be taken to the Willows Rock Stack (“WRS”) at the northern end and the Polishing Pond stockpile at the southern end. Management of the rock material within these stockpiles will be to reduce oxygen and water ingress, to prevent as much as practicable the oxidation of materials and to reduce the mobilisation of contaminants. Water from these stockpiles will be managed so that it is captured and taken to the WTP for treatment and discharge. Water encountered during the tunnel construction will be drained to sumps. Water not recycled for drilling purposes will be pumped via the mine services to the WTP for treatment and discharge. 5.4 WATER An assessment of the likely effects on water associated with development of the Waihi North Project tunnelling system is provided in GWS (2022a), a copy of which is provided in Part H of these application documents. A summary of the key findings of the GWS assessment is provided below. 5.4.1 Potential Effects on Surface Water Groundwater modelling has been undertaken to assess the effects of the tunnel on the near surface environment. The modelling has indicated that once the tunnel is 20 to 30 m below the ground surface depressurisation effects are limited to the rock mass surrounding the tunnel with no connection with the surface or shallow groundwater system expected. Given that the southern portion of the tunnel decline is already dewatered to a depth of approximately 70 m below the ground surface (in association with existing mining at activities in this area), and the tunnel will continue to be driven at a depth greater than that, no further drainage effects are expected in the near surface. Therefore, the potential for effects on streams and springs is considered to be negligible. 5.4.2 Effects on Groundwater and Groundwater Users The assessment indicates that up to 3,000 m3/d groundwater will be taken from the Waihi Basin catchment during construction of the access tunnel. This water will ultimately be captured and returned to the catchment via the WTP. The Waihi Basin aquifer management area which the access tunnel is located within, is divided into the Waihi Basin shallow aquifer system (0.5 m to 30 m depth) and the Waihi Basin deep aquifer system (>30 m depth), however the resources are managed as one integrated system.
RkJQdWJsaXNoZXIy MjE2NDg3