B-1 - Area 1, Coromandel Forest Park – Assessment of Environmental Effects 72 ingress occurrences are suitably adapted to address any deviations from expected conditions; Implementing dewatering measures, drainage and depressurisation in mine areas only when pathways are sufficiently sealed; Assembling and adhering to suitable Trigger Action Response Plans during mining so that methods of mitigation to control groundwater ingress occurrences are suitably adapted to address any deviations from expected conditions, including implementing secondary and tertiary grouting or other mitigation measures where necessary; and Having available, when required, the equipment and suitably qualified and experienced personnel to conduct appropriate monitoring and testing, implement grouting requirements or alternative mitigation measures. The proposed conditions in Part F of these application documents provide a detailed roadmap for how the principles described in the Valenza report will be applied to ensure an acceptable outcome is achieved in respect of effects on surface water. 5.3.3 Warm Spring Cessation It is expected that the warm spring discharging from the East Graben vein on the southern side of the Wharekirauponga Stream bank will cease for the duration of mining, resulting in an estimated loss of surface water flow of approximately 3 L/s. Based on the May 2020 low flow gauging event at WKP1 of 68 L/s this loss would represent <5 % of the catchment baseflow. It is noted, however, that gauging site WKP1 does not include flows from the subcatchment to the north of Wharekirauponga, so the effect on the total catchment water balance would be less than that and likely within the accuracy of the gauging. Given the higher mineral load of the spring discharge compared to surface waters, the quality of the stream water may improve modestly as a result of the spring discharge ceasing. 5.3.4 Effects on the Soil Regolith and Plant Growth Aside from deep groundwater inputs to surface waters, interflow from Regolith soils is the other input to surface waters and is by far the most dominant input. Based on the gauging undertaken, interflow could contribute 90 % of the surface waterflows. This water will continue to discharge into the catchment and will be unaffected by mining as it is a function of climatic conditions and sits in the unsaturated zone above the permanent water table as shown in Figures 29 and 30 below.
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