| Stormwater Philosophy | Stormwater Management Plan | 2210835-1190907474-109 | 21/06/2022 | 2 Sensitivity: General ● Flood maps of the Ohinemuri River catchment, obtained via the Waikato Regional Hazards Portal do not indicate flooding within the vicinity of the site, nor the Mataura Stream catchment. At this stage, it is assumed that there are no downstream flooding issues. ● A 24-hour rainfall distribution has been adopted for peak flow control criteria as per WRC TR20-07, Section 7.1.7. ● Management of stormwater within the WRS catchment, and sizing of the WRS collection pond is excluded from this report, as this is covered by the GHD Water Management Studies report (refer Section 5, GHD 2021). ● It is assumed the material at the outlet points to existing wetlands/water bodies is “course gravel” based off the GNS science geology web map (2021) recording the area as “Waiwawa Subgroup andesite and dacite of Coromandel Volcanic Zone”. However, separate ecological, and soil studies are being undertaken (currently being procured by OGNZL) that will inform the value to be adopted at later design stages. ● The design will be refined and updated in subsequent design stages. The intent is outlined within the report. Referenced Reports: ● WKP Mine Technical Description of Infrastructure Life of Mine Report, Beca Ltd., 10/3/2021 (Rev C, Phase 3 addendum) ● Waihi North Project – Water Management Studies, GHD (WAI-985-000-REP-LC-0011_RevC.1 DRAFT), December 2021 ● Willows Road WRS & SIA Geotechnical Assessment, Golder Associates Ltd (WAI-985-000-REP-LC-0037_RevA), December 2021. ● Draft Site Erosion and Sediment Control Plan, Southern Skies Environmentals Ltd., 12 November 2021 ● Draft Waihi North Project, Ecological Assessment, Version 3, Boffa Miskell Ltd., 20 December 2021
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