conversation with ge, page-18

I didn’t discuss this specifically, but I have previously raised the topic. For the benefit of those who don’t understand hydrogeology – and by no means am I an expert – the following diagram provides an excellent overview of the ‘conditions’ being experienced at the mine. Please note this is an inaccurate representation of actual, but illustrates the conditions:

Conceptually the mine is at three (3), with the bores drilled down the pit floor at four (4). As previously mentioned some of the mine water ingress comes from surface ingress and direct ingress due to rain. Approx. 17% comes from this source. The balance (83%) is from underground inflows which have currently been drawn down to below the water table. The underground inflows come from a very large aquifer (underground), which seeps up through the porous ground rock. The exact path and size is not known which is not unusual as they cant map the entire geology. What is known is the depth – well below the planned mine floor. This does not include future underground workings, but it’s a moot point because no one at this point knows how deep and exactly what direction the underground workings will take.

I don’t know the exact flow rates during the ‘wetter’ seasons. However, the aquifer is only an issue as it swells up through the surface ground rock. This only happens during severe rainfall when it ‘recharges’, swells and pressure forces the water up. The underground dewatering and depressurising bores counter such events and the overflow is pumped up and out into a separate pit. The aquifer is ’constant’, but as I said it only becomes a problem when it swells. However, the dewatering design and equipment have been designed to deal with such events. Additionally, the aquifer has natural drainage points, so as time elapses without rain/recharge, the water levels empty into localised lakes, streams and the sea. i.e flooding in the mine is only temporary, the pumping systems just hasten and/or prevent water collection.