The following table shows the mean values of chemical analysis of the water supply from the Gear Island Water Treatment Plant, from 1 July 2019 - 30 June 2020, 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 Mean value Max value Alkalinity - total g CaCO3/m³ - 1 48 48 Aluminium - total g/m³ 0.1 (B) 2 0.021 0.021 Arsenic - total g/m³ 0.01 (A) 2 <0.002 <0.002 Boron - acid soluable - 2 0.02 0.02 Cadmium - total g/m³ 0.004 (A) 2 <0.001 <0.001 Calcium - Acid Soluble g/m³ - 2 18.25 19.4 Chloride g/m³ 250 (B) 2 16 16.8 Chromium - total g/m³ 0.05 (A) 2 <0.001 <0.001 Conductivity at 25°C mS/m - 1 17.5 17.5 Copper - total g/m³ 2 (A) 15 <0.013 <0.013 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) 15 0.056 0.105 Lead - total g/m³ 0.01 (A) 2 <0.001 <0.001 Manganese - total g/m³ 0.04 (A) 15 0.001 0.001 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 0.53 0.61 pH 7.0-8.5 (B) 1 7.7 7.7 Selenium - total g/m³ 0.01 (A) 2 <0.005 <0.005 Silica g/m³ - 2 15.45 17.7 Sulphite g/m³ 250 (B) 2 6.39 6.59 Total dissolved solids g/m³ 1000 (B) 1 86 86 Zinc - total g/m³ 1.5 (B) 15 0.011 0.016