WAI-985-000-REP-LC-0056 Revision 0 Page 17 of 21 Waihi North Project – Tailings and Rock Storage – Functional Need Assessment 4 GLADSTONE OPEN PIT The proposed GOP is a new open pit mine located southwest of the existing Processing Plant, centred over Gladstone Hill and part of Winner Hill. The proposed GOP will provide access to an ore resource of approximately 2.59 million tonnes / 130 thousand ounces of gold and provides material to construct TSF3 and GOP TSF. Open pit mining is required to extract the gold economically. Underground mining would not be feasible. Further to providing an additional ore resource the GOP provides suitable material required to construct the downstream embankment for TSF3. GOP produces 18.7M tonnes of overburden material i.e. earth and rock fill. Of this, GOP provides approximately 4.3Mt non-acid forming (NAF) rock for construction. Along with the NAF material excavated from the NRS and TSF3 foundation undercut works sufficient NAF is provided for the TSF3 and NRS foundation and encapsulation layers, as well as material for construction of the perimeter drains and embankment. MOP4 (the consented further expansion of Martha Pit) as an alternative source of material for TSF3 construction does not provide sufficient material for constructing TSF3. The material for MOP4 is primarily PAF, with only limited NAF material available. GOP was optimised to target the mineral resources and provide sufficient rock for TSF3 construction, taking into account the relevant geotechnical, geochemical and hydrogeological conditions present within Gladstone hill. Open pit mining of Gladstone ore body allows the opportunity for the pit shell to be converted to a TSF on completion of mining. GOP TSF can provide 2.1M tonnes of capacity. The proposed in-pit disposal requires no additional land disturbance and allows for the pit to be backfilled for closure. As an alternative option Martha Open Pit as a TSF was considered. Current ongoing mining of MUG beneath the pit makes this impractical and presents a safety risk to the MUG operations. As noted above, the Waihi North Project requires 8.66M tonnes of tailings storage. Of this, 6.8M tonnes capacity is provided by the proposed TSF3 and Gladstone provides 2.1M tonnes of capacity, giving the capacity required and a small margin for additional storage if required. In summary, there is no viable other way to access the Gladstone orebody that avoids consuming the upper extent to the Gladstone headwaters, and open pit mining of GOP provides the materials to provide sufficient TSF storage for the WNP.
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