B-2 – Area 2 - Assessment of Environmental Effects 65 will be able to be developed in a manner which ensures that the proposed surface infrastructure at Willows Road is geotechnically sound. 5.9 GEOCHEMISTRY AND ACID ROCK DRAINAGE An assessment of geochemistry matters relating to Area 2 is provided in GHD (2022), a copy of which is provided in Part H of these application documents. The WRS facility will provide for storage of PAF and NAF rock. The PAF rock requires a carefully laid out management strategy that mitigates acid generation and leaching potential. This will involve the WRS being established on a low permeability footprint, provision of subsurface drainage to collects and divert seepage to the Main Collection Pond for appropriate treatment, and addition of crushed limestone to the PAF rock to increase its acid neutralising capacity to prevent long term infiltration of oxygen and water. This is the same approach used and shown to be effective in the construction of the existing TSFs and rock stacks by OGNZL at Waihi. 5.10 EFFECTS ON WATER 5.10.1 Effects Due to the Construction and Operation of the Willows Road Access Tunnel and Portal An assessment of the likely effects on groundwater 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. Key conclusions of the GWS (2022a) report are: Any baseflow loss to Mataura Stream will be of such a small scale that it would not have discernible effects within the surface water body; There will be no discernible effects on any neighbouring bores; The potential effects on other aquifers will be less than minor; No adverse effects on groundwater quality are expected from the tunnel; and Soil moisture conditions in the regolith soils or terrace deposits in the near surface from which plants draw water are not expected to change as a consequence of dewatering the deeper rocks. 5.10.2 Effects of Constructing the Surface Facilities During construction and bulk earthworks erosion and sediment control will be required. The proposed measures are described in the report prepared by Southern Skies (2022) and provided in Part H of these application documents. These measures are incorporated into the proposed consent conditions.
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