www.valenza-engineering.com 381_R_04_Rev 0 OGNZL_WUG_Phase1_Conceptual_Mitigation 6 3. PREVIOUS STUDIES Previous groundwater related studies during 2020 and 2021 have focused on several key matters required to allow the WUG mine development to proceed. These are notably: • Development of the twin access tunnel (exploration drive). Selection of alignment. Groundwater effect. Requirement for resource consent for the WUG to allow construction to proceed. • Effects of tunnel construction on surface water systems and their management such that there is no measurable change in the natural flows or water quality of surface water systems and no measurable dewatering of the soil Regolith which could have an adverse effect on vegetation. • Effects of mine development and mine operational dewatering on surface water systems and their management such that there is no measurable change in the natural flows or water quality of surface water systems and no measurable dewatering of the soil Regolith which could have an adverse effect on vegetation. • Groundwater and surface water testing and monitoring. Monitoring wells, water quality sampling, hydraulic tests (packer), streamflow gauging, and stream level logging. • Conceptual modelling. Geological model development. Numerical modelling (in progress). 3.1. ACCESS TUNNELS The access tunnel extends in two sections, the Willows Access Tunnel from the Willows Farm portal to the orebody, and the WUG Access Tunnel from the processing plant to the junction with the WUG access tunnel. Overall, the access tunnels extend northward from a portal close to the processing plant north of Waihi township for 6.8km, terminating in the WUG mine at the location of Ventilation Shaft 1. The tunnel is single-bore over the 1.3km WUG section northward from the processing plant portal up to the boundary of the CFP, and twin-bore for the remaining 5.5km from the point where it is joined by the Willows Farm extension. The Willows Farm access tunnel exits at a road head portal on the CFP land boundary. The tunnel alignment is shown in Figure 3-1 and in Appendix A Figure 1 (Site Overview). The portal is at an elevation of 180masl declining to -10masl at 1.5km chainage and then gently climbing to 50masl towards its termination in the WUG. These elevations place the tunnel invert level at between 150 and 275mbgl (at its maximum below the crest of the Coromandel Ranges). Alignment selection was based on OGNZL land ownership, geotechnical considerations, and minimising disturbance or nuisance to property, amongst other factors (Golder ref 3). GHD developed a Conceptual Geological Site Model (CSM) in late 2020 (GHD ref 2). Originally described as the WUG Exploration Tunnel, this was intended to allow additional mineral resources, geotechnical and hydrogeological drilling and testing from an underground position, where access from the surface was restricted by the current conditions of access to the conservation land.
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