B-5 – Area 5 - Assessment of Environmental Effects 188 Discharge Receiving Environment Alternative Methods of Discharge catchment, with an ideal ratio of 3;1, but not exceeding 5:1. The spillways have been designed to safely convey 1% AEP events. During events of this magnitude, overflow from the sediment retention ponds can spill flows into the adjacent waterbodies with limited adverse environmental effect due to the higher flows and mixing capacity of the waterbodies. Designing to a large capacity would therefore provide limited additional environmental benefit and was not considered further. Discharge overburden to land within topsoil stockpiles and to create perimeter earth bunds. Refer to Section 2of this AEE. The storage of overburden needs to be discharged to these locations for operational reasons. To discharge overburden to land within GOP to create the GOP TSF. Refer to Section 2 of this AEE. Alternative options for the disposal of overburden have been considered by EGL(2022a). To discharge overburden to land to backfill the in-pit TSF for rehabilitation. Refer to Section 2 of this AEE. Alternative options for the disposal of overburden have been considered by EGL(2022a). To place overburden and PAF into land to backfill the Gladstone Portal and decline for rehabilitation post mining activity. Refer to Section 2 of this AEE. Alternative options for the disposal of overburden have been considered by EGL(2022a). Overall, however, it is normal practice to backfill voids created by underground mining. To discharge overburden material, ore and limestone to land in stockpiles within the Waihi Surface Facilities Area. Refer to Section 2 of this AEE. This is a continuation of the existing discharge approach authorised by resource consents AUTH91295 and 109744. As this approach has not had any demonstrated adverse effects on the environment, as confirmed by OGNZL’s extensive monitoring in this area, no further alternatives were considered. To discharge treated water from the WTP into the Refer to Section 2 of this AEE. This is a continuation of the existing discharge approach authorised by resource consent AUTH971318.01.13. As this approach has not
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