B-6 – Area 6 – Assessment of Environmental Effects 20 The site lies above rhyolite, dacite and ignimbrite, beneath which varying thicknesses of volcaniclastics, hydrothermal vent breccia, then andesite rock. The site’s topsoil generally ranges from 0.1 m to 0.4 m thickness. Figure 10: NRS geology - east-west cross-section. Rhyolite (orange), dacite (light purple), ignimbrite (grey), andesite (light pink) (GHD 2022b). 2.13 HYDROGEOLOGY The hydrogeology of Area 6 is described in Section 5 of EGL (2022d) and Section 4.3 of GHD (2022b), copies of which are provided in Part H of these application documents. The geology beneath Area 6 shows no clear separation of shallow and deeper groundwater systems. This is due to the presence of multiple alluvial paleochannels within and overlying variable volcanics (ignimbrite, dacite and rhyolite). Overall, it is interpreted that the groundwater systems are hydraulically connected and collectively discharge to the Ohinemuri River west of the NRS. 2.14 HYDROLOGY The hydrology attributed to Area 6 is described in Section 7 of EGL (2022d) and in Section 3 of GHD (2022), which are provided in Part H of these application documents. Area 6 is contained within the TB1 catchment, which is a sub catchment of the Ohinemuri River. TB1 drains a catchment of approximately 112 ha and runs northwest to join the Ohinemuri River north of the Frendrup Gauge (see Figures 11 and 12). TB1 was substantially modified when the Northern Stockpile was constructed with the footprint of those works extending over its original alignment.
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