www.valenza-engineering.com 381_R_04_Rev 0 OGNZL_WUG_Phase1_Conceptual_Mitigation 47 • Installation of dual standpipe piezometers similar to the current approach (WKP-P01S/D Shallow/Deep, WKP-P02 etc) as presented in Flo Solutions Data Gap Analysis and Field Program Recommendations 20); • From the results of the monitoring completed, and in compliance with the OM, confirm the existence and extent of the multi-aquifer system and role of EGV for connectivity and confirm the modelling, design and dewatering concept; and • Based on the criteria defined from the findings of the NM, define alert levels for each zone and parameter at specific phases of the development. Parameters would include instantaneous flow rates/hole, per 100m long section of tunnel, pore pressure, drawdown, chemistry and temperature. 8.3. OPERATIONAL PHASE Operational monitoring will include the following elements: • Measurement of inflow rates within the mine workings at a frequency adapted to the development rate (daily to bi-monthly max). Conduct water quality sampling to characterise the potential differentiation of groundwater (hydrochemical characterisation); • Completion of an active mine water balance to assess inflows in zones according to model predictions with a feedback loop to allow regular model re-calibration and revised inflow predictions: • Conduct ongoing testing, sampling and probing (to be defined as part of an operational Groundwater Monitoring Plan developed based on the NM findings and mine planning); and • Installation of pressure gauges underground and confirmation of the evolution and extent of the depressurisation at the surface. Trigger TARPs action plan if results are exceeding criteria. 8.4. CLOSURE AND POST CLOSURE PHASE Closure and post-closure monitoring and testing will include the following elements: • Development of a hydrochemical forward analysis assessing the post closure water quality within the mine void and potential impacts on surrounding receptors once, at the end of the recovery phase when static level is attained, and mine-water discharge re-occurs through natural pathways (springs and seeps); and • Measurement of recovery rates within the mine workings at a frequency consistent with the modelled recovery rate. Conduct sampling to confirm the water chemistry considered in the hydrochemical forward analysis.
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