EGL Ref: 9215 23 June 2022 Page 18 This report shall only be read in its entirety. File: WAI-985-000-REP-LC-0002_Rev0.docx. of 10. Ore associated with the Waihi North Project is proposed to be pumped at about 45% solids by weight. 4.2.4. Tailings delivery and discharge Tailings are pumped as a slurry from the Process Plant into Storage 1A TSF through rubber lined steel and polyethylene pipelines. Two 250 mm diameter pipelines are used to deliver the tailings slurry from the Process Plant to the TSF. The pipelines are contained within open trenches or bunds, which act as a containment device in case of a pipeline rupture or spill. The trenches divert any spill towards collection ponds or tailings ponds. Each pipeline is pressure tested annually to confirm its operability. There are two 90 kW variable speed Warman primary slurry pumps. Booster pumps are located along the pipelines. Currently the tailings are pumped into Storage 1A over a plan distance of 1,750 m and elevation change of +74 m. Historically tailings were pumped into Storage 2 over a plan distance of 1,000 m and elevation change of +56 m. Tailings have typically been discharged via spigots, but end pipe discharge has been used at some times during the operation of Storage 2 and 1A. Tailings are deposited over short sections on a rotational basis to allow resting and drying. The pond water level is maintained low during operation to expose as large an area of tailings as possible to air-drying. Air-drying has the benefit of achieving higher density and strength. The deposition of tailings onto a beach (subaerial deposition) via spigots promotes segregation of the tailings. The coarsest tailings generally settle out closer to the point of deposition, with the finer fraction (slimes) transported further. The deposition of tailings on a rotational basis result in local variations in tailings characteristics both in between spigots and transverse to the embankment crest. Changes in ore characteristics can also affect the characteristics of the tailings. FIGURE 11: TAILINGS BEACH IN STORAGE 1A
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