19 August 2020 Rory McNeil Project Manager OceanaGold Limited Our ref: 125/336/58 Your ref: Dear Rory WKP Exploration Tunnel - Water Assessment Conceptual Geological Model Data Report: August 2020 1 Introduction 1.1 General GHD Limited have been commissioned by OceanaGold New Zealand Limited (OGL) to provide a preliminary Conceptual Geological Site Model (CSM) for the proposed underground exploration tunnel from a tunnel portal located on the Willows Farm block directly north of Waihi township, extending northward for approximately 7 km to terminate underground in the vicinity of the Wharekirauponga (WKP) Stream (referred to as the WKP Tunnel). The development of a CSM is required to provide an initial interpretation of the ground conditions along the alignment of the tunnel to support both the surface water and groundwater assessments of effects associated with the proposed WKP Tunnel. 1.2 Scope of Conceptual Geological Site Model The scope of the CSM was to develop a high level geological model. Due to a limited amount of engineering geological subsurface data, no interpretation of engineering geological conditions has been completed at this time. The model has been developed for the following end-use requirements: To support high level 2D groundwater modelling by others (GWS): along tunnel alignment To support high level surface water and surface water geochemistry modelling As such, the following features have been given focus: Significant faults / lineaments that are identifiable from surface mapping – likely to locally effect subsurface permeability’s and hydrothermal alteration/mineralisation Known rock-water hydrothermal alteration zones, with focus given to those that have an effect of groundwater permeability values (argillite sequences and silicification/quartz replacement).
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