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