B-5 – Area 5 - Assessment of Environmental Effects 24 The geology in the vicinity of Gladstone consists of a weathered upper andesite with some hydrothermal breccia included. Young volcanics are present on the eastern and southern flanks of Gladstone Hill. Alluvium is present to the south and west. At the location of the Gladstone wetland, dacite exists that supports the wetland and forms the neighbouring Black Hill. Two historic landslides are present on the west and north-east sides of Gladstone Hill. The landslide on the west will be stabilised by the proposal because GOP will reduce the height of the western side of Gladstone Hill, consequently reducing mobilising forces for a landslide. The old landslide on the north-east side of the hill will be removed by development of the GOP. 2.13 HYDROGEOLOGY The hydrogeology of the site is described in GWS (2022a) and GHD (2022b), copies of which are provided in Part H of these application documents. Much like elsewhere in Waihi, the groundwater system near Gladstone Hill consists of a shallow groundwater system in young volcanic and alluvium deposits and a deeper system within the andesite rockmass. The systems are separated locally through the presence of low permeability weathered layers. The andesite rockmass host to the Gladstone vein system is already dewatered for the most part due to the Favona underground mine. The vein system in the southwest is only partly dewatered. The site is within the Waikato Regional Plan (“WRP”) defined ‘Waihi Basin Aquifer’. For water allocation, WRC specifies a combined (shallow and deep aquifers) management volume of 6M m³/year3. 48 registered bores are within 3 km of the GOP. Nine have water permits authorising groundwater abstractions. The closest are bore nos. 72_959 and 72_961, being 430 m – 440 m south of the GOP. The closest consented groundwater abstraction site is at bore no 72_9798, at Black Hill Orchard on SH2, approximately 820 m south of the GOP. 2.14 HYDROLOGY The hydrology of the area is described in GHD (2022), a copy of which is provided in Part H of these application documents. The location of Area 5 relative to surrounding waterbodies is shown in Figure 13. 3 WRP Table 3-6: Sustainable Yields from Aquifers.
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