SECTION 3 Site Investigations & Results C:\D Data\GWS C Drive\GWS\Client Files\1344 OGL - WKP\4 Deliverables\WKP Final Draft Report\June Report\WAI-985-000-REP-LC-0030. Final_Rev_0.docx 29 Andesite which will not dewater as a result of mining, and therefore, effects on the stream are not expected. At the intersection of the EG main vein and the Wharekirauponga Stream, a warm spring is present at a discrete location on the stream bank. This spring is formed due to fluids upwelling from the greywacke basement rocks through the main Edmonds Fault mixed with shallower groundwaters. The spring is generally in the order of 20°C and as such is not deemed as being geothermal nor is it related to a geothermal source. The spring emerges at that location due to truncation of the structure by later phase faulting and/or as a contact spring with overlying Andesite rocks. The spring expected to be hydraulically connected to the EG main vein system and as a result of mine dewatering it will cease to discharge into the stream for the duration of mining. The EG vein is formed beneath a ridge that runs subparallel to the Wharekirauponga Stream and is not truncated. Consequently, the main vein is not drained due to the absence of a discharge point. The associated hanging wall vein sets adjacent to the stream are able to discharge groundwater, however, this is at a low rate due to the veins being discontinuous and surrounded by low permeability host rock formed by alteration or weathering. The EG vein is likely to be mined from an elevation of approximately 180 m RL down to -300 m RL, and assuming a groundwater level within the vein at 160 m RL, some 460 m of dewatering would be required to mine the deposit. These metrics are, however, still to be accurately determined and will be verified through the mine design process. The southern extension of the EG vein projects towards the Edmonds Stream headwater springs and dewatering effects in the vein system could potentially affect spring discharge rates if hydraulically connected. The T-Stream vein and associated vein sets are exposed at the surface and the main vein is truncated by the Teawaotemutu Stream. The T-Stream vein is exposed in the stream cutting, allowing groundwater to discharge and is, essentially, drained to this elevation (approx. 180 m RL) or possibly even lower. The vein acts as a conduit for groundwater discharge. The T-Stream vein is likely to be mined down to an elevation of around -100 m RL meaning some 280 m of dewatering within the vein would be required to mine the deposit. West of the T-Stream vein is the Western Rhyolite dome that is host to another smaller vein system. At this location the headwater springs discharge into the Teawaotemutu Stream. Conceptually this vein system is hydraulically disconnected from the other vein systems due to the low permeability host rock and as such, dewatering effects at that location are expected not to develop. This assumption does, however, require further assessment.
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