www.valenza-engineering.com 381_R_04_Rev 0 OGNZL_WUG_Phase1_Conceptual_Mitigation 49 These techniques are commonly used in the industry and their application is not expected to represent a challenge for the WUG project. The concept defined in this Phase 1 report will be refined once the numerical model is completed in the following phase of work (Phase 2), which includes the development of a Mine Water Management Plan with defined appropriate trigger levels and action plan. This document will become key to the safe and cost-effective dewatering of the mine. In the interim between Phases 1 and 2, field installation and testing programs will be completed to address the current knowledge gaps that will allow the level of uncertainty with regard to the understanding of subsurface and deeper groundwater and surface water inter-connectivities to be reduced. Imperatively, this is founded on the activity being managed to achieve ‘no measurable effect’ compliance limits in terms of its effects on surface water and shallow groundwater. The current Phase 1 conceptual level assessments of the impacts on surface water systems have identified significant data gaps that will require closure to enable accurate pre- and post-mitigation predictions to be made from the numerical modelling. This relates primarily to the characterisation of the connections between the surface aquifer, headwater springs and stream baseflow with the deep groundwater system present in the mine and tunnel areas. It is recognised that access constraints may not allow these data gaps to be fully closed and that necessarily a significant reliance on observational approaches to the tunnel and mine development will remain at the current pre-feasibility level of study.
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