GHD | Oceana Gold New Zealand Ltd. | 12552081 | Waihi North Project 17 2.4.1 In-stream Compliance Table 5 summarises Ohinemuri River in-stream water quality at two sampling locations, OH5 and OH6, over the period January 2019 – March 2021. The tables show that the Ohinemuri River water quality is currently within the compliance criteria for all relevant parameters. Table 5 Ohinemuri in-stream water quality at sample locations OH5 and OH6 OH5 OH6 Consented Receiving Water Quality Chemical Parameter Mean Max Mean Max Hardness 20 g/m3 CaCO3 Hardness 100 g/m3 CaCO3 pH 7.3 8.8 7.1 8.5 6.5 – 9.5 Temperature (°C) 17.0 24.3 16.9 24.2 <3°C Rise Cyanide (g/m3) 0.002 0.005 0.002 0.002 0.093 0.093 Iron (g/m3) 0.09 0.23 0.08 0.21 1.0 1.0 Manganese (g/m3) 0.01 0.05 0.02 0.08 2.0 2.0 Copper (g/m3) 0.001 0.012 0.001 0.010 0.003 0.011 Nickel (g/m3) < 0.0005 < 0.0005 0.0005 0.0010 0.04 0.160 Zinc (g/m3) 0.002 0.005 0.003 0.008 0.027 0.100 Silver (g/m3) < 0.0001 < 0.0001 < 0.0001 < 0.0001 0.00025 0.00284 Antimony (g/m3) 0.001 0.004 0.001 0.003 0.030 0.030 Arsenic (g/m3) < 0.001 < 0.001 < 0.001 < 0.001 0.19 0.190 Selenium (g/m3) 0.001 0.005 0.001 0.005 0.02 0.020 Mercury (g/m3) < 0.00008 < 0.00008 < 0.00008 < 0.00008 0.000012 0.000012 Cadmium (g/m3) 0.00005 0.00005 0.00005 0.00005 0.0003 0.001 Chromium VI (g/m3) < 0.01 < 0.01 < 0.01 < 0.01 0.01 0.01 Lead (g/m3) 0.0001 0.0002 0.0001 0.0003 0.0004 0.0025 TSS (g/m3) 5 220# 5 230# +10 g/m3 compared to upstream where upstream < 100 g/m3 or <10% increase Ammoniacal N (g/m3) 0.2 1.0 0.2 0.7 0.189 – 3.01 Major Cations / Anions Ca2+ 71 160 81 169 N/A Mg2+ 7 15 8 21 N/A Na+ 18 36 21 50 N/A K+ 4 7 4 9 N/A SO4 2+ 206 410 244 520 N/A *Trace element concentrations are dissolved *Where all samples of the monitoring period were below the mdl, the concentration is given as <mdl. Otherwise the mdl is used as the concentration for the specific sample #Values are reflective of high sediment load upstream of the site discharge 1. Dependent on temperature and pH. Refer to Table 2 of RC 971323 (and RC 971285, 971311, 971312, 971303-971306). Consent refers to Total Ammonia.
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