www.valenza-engineering.com 381_R_04_Rev 0 OGNZL_WUG_Phase1_Conceptual_Mitigation 18 of the baseflow in the Waiharakeke Stream, this amount of stream water loss would likely be indiscernible and temporary. 5.1.4. FLOSOLUTIONS ANALYTICAL MODEL (APRIL 2022) As part of FloSolutions’ conceptualisation and modelling scope, an analytical modelling has been developed in AnAqSim (Fitts Geosolutions) as a preliminary assessment of the potential for stream capture in response to the development of the underground mine workings (FloSolutions, ref 17). The analytical approach adopted, whilst significantly different and simplified compared to the future modelling work to be undertaken in the following stage of numerical modelling, provides a preliminary evaluation of drawdowns within the mine area. It is noted that the AnAqSim model area corresponds to one portion of the study zone only (the upper portion of the Wharekirauponga catchment defining an area of 11.4km2) and excludes the tunnel alignment due to the low impact that the project has on this region. The simulations undertaken were supported by a two-fold sensitivity analysis, assessing the influence of stream conductance (unknown at this stage of the study) on model performance and modifying permeability values to mimic the effect of mitigation methods during mining. The scenarios modelled are presented in Table 5-1. Table 5-1:Scenarios simulated in AnAqSim (after FloSolutions April 2022, ref 17) Simulation ID Scenario Detail 0 Base Model 1 Simulation of underground workings as drains with the conductance of 0.1 2 Simulation changing river conductance by 1 order magnitude higher and keeping the underground working as drains (C=0.1) 3 Simulation changing river conductance by 1 order magnitude lower and keeping the underground working as drains (C=0.1) 4 Simulation of underground working as drains and increasing the K of Lower Core EG and Lower Footwall by 1 order magnitude to simulate possible fracture opening and enhanced permeability due to mining 5 Simulation of underground working as drains and decreasing the K of Lower Core EG and Lower Footwall by 1 order magnitude to simulate a possible mitigation scenario
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