June 2022 G-14642.71-006-R-Rev0_FINAL 45 11.0 RECOMMENDATIONS Targeted subsurface investigations, such as boreholes at shaft locations, are recommended to supplement the currently available geotechnical information between Willows Road farm and WUG. In addition, drilling ahead of the tunnel face will be important for predicting ground conditions ahead of the tunnel face for support and design of groundwater management, as well as geological exploratory information. Further investigation of in situ stress as part of detailed design of the tunnel. Consider potential elevated groundwater temperatures affecting the underground works. Hydrothermal alteration has widely affected the rock mass at the site, including placement of the WUG orebody. We are not aware of any evidence of on-going hydrothermal processes affecting the area; however, some inflows of hot groundwater are possible. Consider the potential effect on design of generally low strength of the rock mass, groundwater conditions and stress conditions. It is anticipated that squeezing ground may be present in areas of very weak ground. Develop measures to ensure that portal security is maintained. Such measures should include management of surface water and shallow groundwater and local support measures such as shotcrete and bolts or a mass gravity wall. Consider the potential adverse effect of acidic water quality on ground support and underground infrastructure.
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