GHD | Oceana Gold (New Zealand) Ltd | 12552081 | Waihi North 93 5. Tailings Storage Facility Three 5.1 Site overview 5.1.1 General site setting A high-level site layout plan of the proposed TSF3 is provided in Figure 5.1. It will extend over a short valley, approximately 700 m wide, covering existing farmland, which comprises surficial alluvium and underlying weathered rhyolite deposits. The hills surrounding the site are remnants of the ancient Ruahorehore Volcanic Dome, which has a maximum elevation of 1,260 mRL. The valley runs approximately from northeast to southwest, down to 1,109 mRL at the toe of the proposed TSF. At this location, the Ruahorehore Stream has a large catchment (580 ha), extending to the east and is heavily altered to form a drainage channel for farming purposes. The site is characterised by generally poorly drained soils (observed boggy surface and surface water ponding in winter). A series of short upper valley branches extend into the hills to the north (Figure 5.2), with two spring-fed streams forming the Ruahorehore Tributary. The tributary flows from the hills via farm drains to the Ruahorehore Stream to the south. The farm drains are shallow with typically very low to no flow baseflow. The Ruahorehore stream will require diversion at the toe of the embankment as indicated on Figure 5.1. The transition from farm drain to stream occurs in the area west of the red catchment marked on Figure 5.1. Shed Spring is located downgradient of TSF3 and immediately south of TSF1A. This spring provides a significant portion of the flow to the Ruahorehore Stream at this location (discussed further in Section 5.3.5). Drainage water from TSF1A toe (GWS, 2019; 2020), springs and farm drains are also inferred to report to Ruahorehore stream downstream of the TSF3 site. Figure 5.1 TSF3 site layout plan showing the Ruahorehore Steam Catchment (red) upstream of the embankment toe
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