GHD | Oceana Gold (New Zealand) Limited | 12537997 | Gladstone Pit TSF 15 2.4.4 Gladstone Hill wetland A wetland is located to the south of Gladstone Hill as shown in Figure 7. Historic images (Figure 7) presented by GWS (2021) suggest the wetland is not natural and has developed because of human disturbance in the area. GWS (2021) discussed the implications of the mining of GOP on the flows to the wetlands. Monitoring of flows indicate that the contributions of Gladstone Hill to the wetland catchment is small and an approximate 3% reduction in flow to the wetlands is expected during mining. Flows will be restored to the wetlands post-mining through a water shedding cover and closure spillway channel. Figure 7 Development of the Gladstone Hill wetland with time 2.5 Geochemistry 2.5.1 Background A geochemical assessment of the ore, tailings, and overburden for the Waihi North Project is described in AECOM (2021). Multi-element analysis, static testing, kinetic testing and column testing were used to characterise ore and overburden samples from selected boreholes distributed across the mining areas. The principal findings are summarised in this report and their impact on closure design (construction, schedule, environmental protection actions, etc.) discussed. 2.5.2 Overburden As described in Section 2.2.1, the mineralised overburden types at Waihi are mainly Andesite, Quartz Andesite and Hydrothermal Breccia. Overlying the Andesite, a series of non-acid forming (NAF) overburden are generally encountered, i.e., Ignimbrite, Dacite, Volcanic Ash and Alluvial Sediments.
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