www.valenza-engineering.com 381_R_04_Rev 0 OGNZL_WUG_Phase1_Conceptual_Mitigation 19 The scenarios considered can be synthetically described as follows: • Scenario 0: Base case (current) • Scenarios 1 to 4: Mine development using a range of sensitivity, without applying any mitigation measures • Scenario 5: Mine development applying mitigation measures aiming at reducing the hydraulic conductivity by an order of magnitude (applying grouting for example). The preliminary results obtained using the analytical approach indicate that the maximum drawdown obtained for scenarios 1 to 4 (without mitigation measures) ranges between 14 and 24m, with a radius of influence greater for scenarios 3 & 4. The preliminary result for Scenario 5 (using K reduction techniques), indicates that the maximum drawdown would decrease to around 13m, with a restricted cone of depression. These preliminary results confirm the suitability of the mitigation measures treatment approach developed within this report. 5.2. GEOLOGICAL MODEL OGNZL maintain a Leapfrog geological model containing the drilling resource and geotechnical data. The principal layers incorporated into this model include 10 lithologies, vein models and structural geology elements. Surface water drainage polylines, LiDAR and sampling locations are included to represent pertinent surface features. 5.3. ENGINEERED MITIGATION MODELLING 5.3.1. UPDATED CONCEPTUAL HYDROGEOLOGICAL MODEL The first phase of the Conceptual Mitigation Study covers the mitigation modelling at a conceptualisation level based on the development of updated conceptual hydrogeological models. A second phase applies the mitigation solutions to a numerically modelled system to determine predictions of the effectiveness of the engineering controls on the surface water system. FloSolutions are providing both conceptual hydrogeological modelling (CHM) and numerical hydrogeological modelling (NHM) to the WUG project. The CHM has been used by VE as a basis to develop the Phase 1 Conceptual Mitigation Model (this report). A common Leapfrog Geo platform is used to represent and analyse the groundwater system and the mitigation systems. The main focus of the CHM is to describe the hydrogeological characteristics of the EGV and T-Stream Vein systems, and their relationship with the shallow groundwater system and with the mine infrastructure. The CHM covers a plan area of 2 km2 over a 600m vertical extent from -300 to 300 masl, covering the WUG mine area within these vein systems. Due to the sparsity of data across the extent of this block and its linearly concentration along drillholes the conceptualisation is concentrated in these alignments. The CHM was provided on 6th April 2022 and the following sections summarise the main elements of the model pertinent to the conceptual mitigation.
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