www.valenza-engineering.com 381_R_04_Rev 0 OGNZL_WUG_Phase1_Conceptual_Mitigation 32 • Monitoring and instrumentation (from the surface and underground locations, using qualitative and quantitative methods, including water sampling, localised pump drawdown tests, pore pressure and mine inflows monitoring). • Probing (pilot hole before development using directional drilling methods and advanced probing during mine development). • Targeted pre-development grouting from underground development, declines and drives. • Secondary grouting during development, associated with depressurisation (drain holes) and dewatering (sump pumping, dewatering wells equipped with submersible pumps). These techniques are commonly used in the industry and their application is not expected to represent a technical challenge for the WUG project. However, challenges will present themselves to accommodate the grouting infrastructure (e.g., cuddies at specific locations) and additional associated costs within the project design and construction. 6.2. GENERAL MITIGATION AND CONCEPT BY ZONE 6.2.1. WUG AND WILLOWS FARM ACCESS TUNNELS The WUG single tunnel extends from the processing plant connecting with the twin tunnel towards the mine from the junction with the Willows Farm single tunnel. The Willows Farm vent shaft is positioned close to the edge of the CFP boundary. The dual tunnel from the edge of the CFP northwards to the WUG orebody contains several additional declines that allow access to the lower parts of the orebody. Monitoring, probing, progressive grouting and depressurisation are expected to be used in these areas of the mine following the sequence below: 1. Instrumentation, probing; 2. Progressive grouting and depressurisation (localised drainage behind the development face and structures); and 3. Dewatering (sump pumping). 6.2.2. VENT SHAFTS Five vent shafts are proposed as part of the WUG project. The first of these lies within the Willows Farmland and outside the CFP. The four vent shafts within the CFP are to be completed from an underground position using a mechanised raise climber (Alimak). The vent shaft at Willows Farm is assumed to be effectively isolated from groundwater because of the construction stabilisation works required in its construction. Small inflows (seepage) can be expected however no significant drawdown is anticipated. The installation of underground instrumentation and the construction of grouting and dewatering chambers from the base of these shafts are expected to be applicable to these areas of the mine. Monitoring, probing, progressive grouting and depressurisation are expected to be used in these areas of the mine following the sequence below:
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