www.valenza-engineering.com 381_R_04_Rev 0 OGNZL_WUG_Phase1_Conceptual_Mitigation 37 6.4. DEWATERING, DRAINAGE AND DEPRESSURISATION 6.4.1. APPLICATION The installation of dewatering infrastructure is likely to be undertaken from key underground locations. These will be assessed from the NM and the practicality of installation location options. Where required and where not provided by planned infrastructure (e.g., top ore drive), specific drives may need to be developed in anticipation to allow sufficient time for dewatering to occur before the ore drive development (effective dewatering can take several weeks or months). Dewatering will be limited to the absolute minimum required to allow mining to occur. The yield and associated drawdown from deep wells and sumps will be monitored and compared to the simulations results. As such, these will be used for large-scale ongoing testing and data validation during mine operation. Where dewatering yield leads to excessive impact (drawdown and pore pressure changes exceeding the trigger level), further grouting (and potentially reinjection of the removed waters) will be implemented, in compliance with the associated TARPs. The installation of submersible pumps will be completed by competent personnel experienced with the design, construction and maintenance of complete mine water management systems. Figure 6-6: Dewatering and Instrumentation completed from Underground Chambers developed in conjunction with the Declines and Drives (deep dewatering wells are shown in blue dotted lines). 6.5. SEQUENCING AND MINE PLANNING The implementation of the control measures will be integrated into the mine planning and formalised in a Triggered Action Response Plan (TARP). The acquisition of baseline information, the construction of underground chambers, the installation of grout curtain and the effective dewatering and depressurisation will require significant time. Unless these
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