GHD | Oceana Gold (New Zealand) Ltd | 12552081 | Waihi North 19 . – Ruddocks gauge: Measures flow on the Ruahorehore Stream, which forms a significant tributary to the Ohinemuri River. The catchment at this location is approximately 20 km2, with flow ranging from 1,850 – 1,500,000 m3/day, and a median flow of 27,900 m3/day. 2.2.2 Surface water allocation Surface water allocation information was obtained from the Water Allocation Calculator (WRC, 2021a) and from information provided by WRC via email (pers. comm. C Harty 23/11/2021). The WNP sites are located within the Ohinemuri River catchments presented in Table 2.1. For both catchments, the current level of cumulative allocation exceeds that catchment’s allocation limits across all months of the year. Table 2.1 WRC surface water catchment information Catchment WNP sites Catchment size Combined primary and secondary allocable flow Allocation status Ohinemuri at Waihi Terrace GOP, NRS, TSF3 74 km2 0.12 m3/s Exceeds the allocation limits across all months of the year (primary and secondary) Ohinemuri at Frendrups WRS 47 km2 0.08 m3/s Exceeds the allocation limits across all months of the year (primary and secondary) 2.3 Regional geology The complex geology of the area is well documented by Brathwaite and Christie (GNS, 1996), in the Project Martha AEE (OGNZL, 2018 and GWS, 2018a), and in OGNZL annual compliance monitoring reports. An overview of the geology of the Waihi area is shown in Figure 2.4 The Waihi Basin is defined as a structurally controlled depression that is likely part of a former caldera structure. Basement rocks in the region comprise Coromandel Group andesite and dacite volcanic rocks which are present in the form of horst and graben structures (up thrown and down thrown blocks) due to past faulting (Figure 2.3). The ore bodies mined by OGNZL to date, and proposed under WNP, comprise near-vertical quartz veining with elevated permeability within an andesite rock mass of relatively lower permeability. The andesite rock mass is overlain, in part, by younger volcanic materials comprising rhyolitic tephras and ignimbrite flows, breccias and tuffs. Paleosols and sedimentary deposits (alluvium “tm”; Figure 2.4) are occasionally interspersed or located at the base of these deposits. These deposits infill a paleo-valley system between the outcropping volcanic highs. To the east of the Favona-Moonlight Graben, a thick sequence of post mineralisation dacite volcanics overlie the andesite rock, forming Black Hill (Figure 2.4). East of the Golden Valley Fault, a rhyolitic intrusion protrudes through the entire sequence to the east of Black Hill. This rhyolite forms the outcrops and topographic highs and is where the rock and tailings storage facilities are located.
RkJQdWJsaXNoZXIy MjE2NDg3