The following table shows the mean values of chemical analysis of the water supply from the Gear Island Water Treatment Plant, for the year ended 30 June 2018, compared with the maximum allowable value (MAV) or guideline value (GV) for each element as set out in the Drinking Water Standards New Zealand (DWSNZ).
Notes: (A) MAV denotes the maximum acceptable value to comply with the Drinking-water Standards. (B) GV denotes the maximum guideline value in the Drinking Water Standards. (C) Denotes that the results are from a sample point downstream of Gear Island Water Treatment Plant
Parameter DWSNZ MAV (A) GV (B) No of samples Median value Max value Alkalinity - total g CaCO3/m³ - 1 72.000 72.000 Aluminium - total g/m³ 0.1 (B) 2 0.018 0.018 Arsenic - total g/m³ 0.01 (A) 2 <0.002 <0.002 Boron - acid soluable - 2 <0.025 0.030 Cadmium - total g/m³ 0.004 (A) 2 <0.001 <0.001 Calcium - Acid Soluble g/m³ - 2 13.625 17.4 Chloride g/m³ 250 (B) 2 17.050 18.000 Chromium - total g/m³ 0.05 (A) 2 <0.001 <0.001 Conductivity at 25°C mS/m - 1 22.700 22.700 Copper - total g/m³ 2 (A) 19 <0.013 0.015 Cyanide g/m³ 0.6 (A) 2 <0.005 <0.005 Fluoride g/m³ - - - - Hydrogen sulphide g/m³ 0.05 (B) 1 <0.05 <0.05 Iron - total g/m³ 0.2 (B) 19 0.035 0.056 Lead - total g/m³ 0.01 (A) 2 <0.001 <0.001 Manganese - total g/m³ 0.04 (A) 19 <0.013 0.002 Mercury - total g/m³ 0.007 (A) 2 <0.001 <0.001 Nickel - total g/m³ 0.08 (A) 2 <0.001 <0.001 Nitrate - nitrogen g/m³ 50 (A) 2 0.720 0.930 pH 7.0-8.5 (B) 1 7.500 7.500 Selenium - total g/m³ 0.01 (A) 2 <0.005 <0.005 Silica g/m³ - 2 16.200 17.400 Sulphite g/m³ 250 (B) 2 6.855 6.890 Total dissolved solids g/m³ 1000 (B) 1 111 111 Zinc - total g/m³ 1.5 (B) 19 <0.013 <0.013