ABN 81 147 114 743 [email protected] www.valenza-engineering.com 381_M_05_Rev0 - WUG Monitoring and Testing Program MEMORANDUM Dear Euan, This memorandum outlines the monitoring and testing programs developed to support the refinement of the conceptualisation and associated numerical models planned during the consenting process. This synthetic document built upon previous reports developed for the project focuses on the measures required to close the knowledge gap and support the proposed mitigation measures strategy. 1. INTRODUCTION OGNZL, a wholly owned subsidiary of OceanaGold Corporation currently operates underground mines in the Waihi area. Future operations comprise the Wharekirauponga Underground Project (WUG) within the Waihi North Project (WNP). The WUG is located 10km north of Waihi township, 150km southeast of Auckland, beneath Crown Land administered by the Department of Conservation (DOC) as a conservation and forest park. The project is currently operated under NZPAM CMA Mining Permit 60541 which allows for mineral exploration activities including surface drilling. Valenza Engineering Pty Ltd (VE) has been tasked by OGNZL to complete an assessment of underground engineered mitigation measures to avoid any impact on surface water systems during dewatering operations associated with mining activities. The scope includes the analysis of the information collated to date by OGNZL and other parties, the development of conceptual mitigation factors (pre-drilling strategy, monitoring, grouting patterns, advised mining methods, dewatering and groundwater control strategies); and provision of advice on the data requirements to implement these measures (VE Phase 1 report, ref 381_R_04, May 2022). The Phase 1 report, as well as reports from GWS (WAI-985-000-REP-LC-0040) and FloSolutions (10222110401-TM-03), have identified data gaps and associated level of uncertainty supporting the collection of additional information aiming at furthering the understanding of sub-surface and deeper groundwater and surface water inter-connectivities. The monitoring program and work sequence summarised in this memorandum aims at closing the following key data gaps: • Surface Water/Groundwater interactions (near-stream data acquisition) • Shallow groundwater system characterisation (aquifer connectivity) • Bedrock aquifer properties (host rock/veins bulk properties) Date: 27 May 2022 Ref: 381_M_05_Rev0 From: Alexis Valenza, Peter Gribbin To: Euan Leslie - OGNZL Subject: OGNZL - Wharekirauponga Underground Project (WUG) – Mitigation Measure Strategy and Baseline Data Acquisition
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