SECTION 1 Introduction C:\D Data\GWS C Drive\GWS\Client Files\1344 OGL - WKP\4 Deliverables\WKP Final Draft Report\June Report\WAI-985-000-REP-LC-0030. Final_Rev_0.docx 1 1. Introduction 1.1 Background OceanaGold Corporation (OGC) are proposing to develop a new underground mine north east of the township of Waihi. The mineral resource is known as the Wharekirauponga deposit. In order to be able to mine the resource from underground, dewatering of the orebody will need to be undertaken and as a result, potential effects on the groundwater system that could develop. OGC has engaged GWS Limited (GWS) to prepare an assessment of effects associated with the proposed dewatering. This report summarises the results of our assessment and is intended to provide sufficient technical information such that it can be included in support of an application for consent to the Waikato Regional Council to take groundwater. 1.2 Project Description A full description of the Waihi North Project is provided in the Assessment of Environmental Effects prepared by Mitchell Daysh Limited. The Wharekirauponga mine will be implemented in two phases, the first phase being the development of the mine access infrastructure. Note that this report does not include effects associated with accessing the ore body through tunnelling. This is described in a separate groundwater effects report for the wider Waihi North Project prepared by GWS (WAI-985-000-REP-LC-0040_RevA.2). An underground mining operation is to be undertaken as the second phase of this project once the tunnel reaches the orebody and appropriate ventilation is established. The construction of the tunnel and ventilation shafts is expected to take 48 months from consent approval, with first stopes expected 8 months later. The mine will have up to four ventilation shafts located above the Wharekirauponga resource within the Coromandel Forest Park and one will be at Willows Farm. Once mining commences, the underground operation involves mining of declines for access to stoping blocks. Access drives will be mined to develop drilling and loading levels, intersecting the orebodies centrally. Ore drives will be developed in both directions along strike from the access drives. Stockpiles will be mined off the decline and in levels for truck loading. Development design profiles have been assumed to be the same dimensions as currently used at Waihi underground operations. 1.3 Scope of Report The scope of this report provides for the assessment of groundwater effects associated with the proposed dewatering of the Wharekirauponga deposit. The purposes of this groundwater effects assessment are to determine: • An estimate of groundwater inflows to the mine • Drawdown effects related to the mine • Potential for effects on groundwater quality • Potential for effects on other aquifers
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