GHD | Oceana Gold New Zealand Ltd. | 12552081 | Waihi North Project 15 2.4 Regime Compliance Table 3 and Table 4 summarise WTP discharge water quality for regimes B and D from January 2019 – December 2020. Regimes A, C and E were not utilised during this period. The tables show that the WTP is currently operating within the compliance criteria as outlined in RC 971318. In most instances the mean (and maximum) concentrations from the monitoring data are well below the compliance values. Table 3 Regime B Discharge Water Quality Range of Concentration Consented Water Quality Chemical Parameter Mean Max Normal Compliance Maximum Compliance pH 8.7 8.9 6.5 – 9.5 Cyanide (g/m3) 0.029 0.06 0.2 0.56 Iron (g/m3) 0.036 0.04 0.8 5 Manganese (g/m3) 0.011 0.019 0.8 1 Copper (g/m3) 0.023 0.066 0.0551 (0.114)2 0.101 (0.258)2 Nickel (g/m3) 0.0014 0.0021 0.941 (2.13)2 Zinc (g/m3) 0.002 0.003 0.611 (1.41)2 Silver (g/m3) 0.00034 0.0007 0.0171 (0.056)2 0.0241 (0.127)2 Antimony (g/m3) 0.0069 0.012 0.1 0.18 Arsenic (g/m3) 0.0016 0.002 1.14 Selenium (g/m3) 0.0088 0.021 0.12 0.2 Mercury (g/m3) <0.000083 <0.000083 0.0005 Cadmium (g/m3) 0.00008 0.0001 0.0071 (0.014)2 Chromium VI (g/m3) <0.01 <0.01 0.06 Lead (g/m3) 0.00018 0.0002 0.0181 (0.064)2 TSS (g/m3) 3 3 8 40 Ammoniacal N (g/m3) 3.04 3.40 1.13 – 18.004 4.98 –209.984 *Trace element concentrations are acid-soluble and based on unfiltered samples 1. Based on a hardness concentration of 530 g/m3 CaCO3. Actual compliance concentrations for these elements vary depending on the recorded hardness in the discharge. 2. Based on the mean and maximum recorded hardness concentrations of 1253 and 1500 g/m3 CaCO3 over the given period. 3. Mercury has a mdl of 0.00008 mg/l therefore the actual mercury concentration is less than given. 4. Dependent on discharge pH and temperature. Consent refers to Total Ammonia
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