GHD | Oceana Gold (New Zealand) Ltd | 12552081 | Waihi North 106 – Permeability of the rhyolite tuff: The scenario testing analysed an order of magnitude higher and lower than the base model K for this rock unit. The results (Figure I.15) showed a change in groundwater flow paths was the key change resulting from the sensitivity tests, which influenced the results as follows: Scenario 3: – A moderate change in tailings volume from TSF3 under Scenario 3, with the lower K value (Sens.5) allowing some tailings porewater (31% of total discharge) to bypass the drains and enter the receiving environment. There was no change reported for the increased K value (Sens.4). – The response of infiltration (which is applied as rainfall recharge) through the embankment was slightly influenced by the underlying rhyolite unit, with a minor increase in embankment discharge under higher K (Sens.4) of 12 m3/day more than the base model; whereas a lower K (Sens.5) decreased by 4 m3/day against the base model. Scenario 5: – The increase and decrease to K both allow for drainage capture of tailings, but a similar order of discharge occurs to the receiving environment. – The same volume of embankment infiltration occurs (as per AECOM 2020), but with the sensitivity test results reporting all captured by drain. Neither analysis results in flow lines to the Ruahorehore Stream from beneath the TSF. Figure I.15 Sensitivity testing outputs for changes to rhyolite tuff K (Sens.4 and Sens.5)
RkJQdWJsaXNoZXIy MjE2NDg3