GHD | Oceana Gold (New Zealand) Ltd | 12552081 | Waihi North 22 . average rainfall (WRC, 2021b), with deeper groundwater and less permeable aquifers in the area expected to be much less than this. Groundwater flow direction through, and discharge from, the deeper volcanics of the Waihi Basin is not clearly documented. Multiple hydraulic divides are documented within the basin (Ling, 2003), with this interpretation expected to be a result of limited deep groundwater data, combined with the complex geology (grabens, faults) characteristics of the region. The Union Horst forms a paleo-topographic high that separates the Martha Graben from the Favona-Moonlight Graben (Figure 2.4). The Union Horst structure is considered to act as a physical barrier between the more structurally permeable areas of the Martha Graben and Favona-Moonlight Graben structures. Prior to the development of the underground mines, the connection of the systems was weak; these are now interconnected due to mine workings and dewatering of Martha underground (MUG) has been more recently used to control dewatering at Favona. Although the site is located approximately 5 km from the east coast of New Zealand, the available data indicates that at the location of WNP, the intermediate to deep groundwater flow at this location is expected to be inland, to the west. For the purposes of this assessment, all groundwater is inferred to discharge to the Ohinemuri surface water catchment, with the volcanic hills to the east of Waihi inferred to provide a groundwater divide between the site and the coast, as defined by the Waihi Basin aquifer boundary on Figure 2.5. 2.4.3 Groundwater management levels The majority of the site is located within the Waihi Basin (WRC WRP Aquifer Map 7; Figure 2.5). The WRS is located just north of the mapped WRC Waihi Basin extent, within an unmapped aquifer. The Waikato Regional Plan aquifer management level for this aquifer is 6,000,000 m3/year, and current available groundwater is reported by WRC to be 30.8% (1,845,000 m3/year) (pers. comm C. Harty, 23/11/2021). WRC treats groundwater and surface resources as being connected and a groundwater take will be considered to reduce the surface water flow downstream of the connected waterways. As noted in Section 2.2.1, the GOP, NRS and TSF3 sites are within the Ohinemuri at Waihi Terrace catchment, and WRS is within the Ohinemuri at Frendrups catchment; both of which are deemed overallocated. Figure 2.5 WRP Aquifer Map 7 (Waihi Basin)
RkJQdWJsaXNoZXIy MjE2NDg3