GHD | Oceana Gold (New Zealand) Ltd | 12552081 | Waihi North 124 Parameter Operational to closure Long-term (post-closure) Co 0.002 0.01 Cr 0.001 0.002 Cu 0.00002 0.0003 Fe 0.6 3.6 Hg 0.00001 0.00002 K 0.6 1.28 Mg 0.3 3.9 Mn 0.09 0.58 Na 11 17 Ni 0.0002 0.002 Pb 0.0001 0.0002 SO4 20 73 Sb 0.00001 0.00003 Zn 0.00004 0.001 Influence on surface water quality – Ruahorehore Stream As outlined in Section 5.5.4, this assessment is presented to provide an understanding of potential effects to the Ruahorehore Stream should leakage from the collection ponds (influenced by embankment rock) enter the stream. The analysis considers 140 L/day of water quality equivalent to embankment rock infiltration entering the stream at low flow (540 m3/day). Such an event would be periodic and limited in timeframe, given that the pond is intended to be emptied when full. The results presented in Table 5.15 therefore represent the most conservative potential scenario for a single point in time. Only minor increases are reported, as denoted by “”. These increases are unlikely to be detected from baseline values within the laboratory analytical margins of error. Table 5.15 Ruahorehore Stream water quality (values in mg/L) Parameter Existing water quality (RU03 and RU10)* Predicted water quality** Receiving water quality criteria Operational Long-term Al 0.01 0.02 0.01 As 0.001 0.001 0.001 0.19 Ba 0.01 0.01 0.01 Ca 3.4 3.5 3.5 Cd 0.00005 0.00005 0.00005 0.0003 Co 0.0002 0.001 0.0003 Cr 0.01 0.01 0.01 0.01 Cu 0.0005 0.0005 0.0005 0.003 Fe 0.1 0.2 0.1 1.0 Hg <0.00008# <0.00008# <0.00008# 0.000012 K 3.0 3.0 3.0 Mg 2.0 2.0 2.0 Mn 0.04 0.04 0.04 2.0 Na 10.0 10.0 10.0 Ni 0.0005 0.0007 0.0005 0.04
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