Technical Memorandum This document is in draft form. The contents, including any opinions, conclusions or recommendations contained in, or which may be implied from, this draft document must not be relied upon. GHD reserves the right, at any time, without notice, to modify or retract any part or all of the draft document. To the maximum extent permitted by law, GHD disclaims any responsibility or liability arising from or in connection with this draft document. The Power of Commitment 12552081 1 May 9, 2022 To Euan Leslie (Oceana Gold NZ Ltd.) Tel 029 335 1207 Copy to Adrian Low (Mitchell Daysh) Email [email protected] From Tim Mulliner (GHD NZ Ltd.) Ref. No. 12552081 Subject Proposed Surface Water Monitoring Conditions – Wharekirauponga Catchment (Waihi North Project) 1. Introduction Oceana Gold New Zealand Ltd. (OceanaGold) have requested GHD New Zealand Ltd. (GHD) provide hydrology advice associated with the potential surface water impacts in the Wharekirauponga catchment associated with the proposed WUG Mine. The purpose of this memorandum is to outline recommendations and recommended consent conditions associated with surface water monitoring within the Wharekirauponga catchment. The scope of this memorandum specifically includes the following items: – Provide advice on future monitoring requirements associated with surface water within the catchment from both a baseline and life of mine (LOM) perspective. – Provide input into draft conditions outlining recommended surface water monitoring requirements to provide robust a baseline dataset prior to the commencement of mining. – Provide input into draft conditions outlining recommended surface water monitoring to enable LOM surface water assessment and consent compliance assessment including the development of trigger values, as well as recommended additional and contingency monitoring associated with breach of trigger values. As part of this assessment a site visit and field investigation of existing and proposed sites was carried out on the 2 May 2022 by Tim Mulliner (GHD) and Lennie Palmer (Riley). The recommendations given here take into account the observations during this site visit and discussion between GHD and Riley on the suitability and practicality of both location and methodology (for surface flow measurement). Provided comments by Riley following the site visit are included in Appendix A. This memorandum is updated from the draft version (dated 13 April 2022).
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