Facts about Napier’s water. There are 481km of piping in the reticulated network. One billion litres pa of water are delivered to residents. Seven bores. Ten reservoirs. 18 pump stations. Napier’s drinking water supply is not fluoridated but has been chlorinated since 2017.
Napier covers an area of 10,560 hectares and, as of 30 June 2017, has a total population of 61,040 people living in 25,429 dwellings.
All of the urban area has a reticulated water supply. Some properties in Taradale still use their own private well supply, however, the City's reticulated supply is available.
A small number of rural properties adjacent to the urban reticulation system have connections to the urban supply for domestic use.
We use a system called SCADA - Supervisory Control and Data Acquisition - to measure the amount of water we use. These are our consumption figures for the past year: 1 June 2017 to 11 June 2017.
|Total Annual Consumption||10,032,280m³|
|Average Daily Consumption||27,486m³|
|Peak Day Consumption||39,408m³|
|Minimum Day Consumption||16,045m³|
Seven bores draw water from the artesian aquifer beneath the City and provide all of Napier's water. The aquifer is part of the Heretaunga Plains underground water system that's administered by the Hawke's Bay Regional Council.
The depth of the wells range from approximately 40 to 100 metres, with the diameters ranging from 200 to 300 millimetres. The aquifer has a static head ranging from approximately one to three metres above ground level.
We have supplied Napier residents with water drawn from bores that meet Interim Bore Security Status standards since 1 July 2018. We worked with bore security experts and contractors to attain the required status: the seven NCC supply bores have achieved the criteria required by the Drinking-water Standards for New Zealand 2005 (revised 2008).
There are eight booster pump stations servicing the City with a total of 25 pumps.
The City has 481km of mains ranging in diameter from 40 to 450mm. The older areas of the City are reticulated with cast iron, and in some cases steel pipes, although these are gradually being replaced as they become uneconomical to maintain. The newer areas were reticulated with asbestos cement pipes until 1986, after which uPVC was chosen as the preferred material.
The Heretaunga Plains aquifer has some of the best water in the North Island and, until recently, did not require treatment. However, a low level E.coli reading in May 2017 saw the Napier water supply chlorinated as a precautionary measure. In July 2017, an independent drinking water assessor revoked the Council's 'secure bore' status, a decision that ensured chlorination had to continue. We then began extensive work on improving the safety of our bores. Prior to these improvements starting, all of our bore heads were below ground. We raised three of the 10 above ground and improved the bore chambers of others. This work was completed in December 2017.
We carry out daily or alternate day testing on our operating bores, depending on the bore status. We also take regular samples from our reservoirs and pipe network to monitor our supply and ensure it meets the Drinking Water Standards of New Zealand 2008.
Napier has never fluoridated its water supply and there are no plans to.
Typical chemical composition of Napier water supply:
However, if tap water is discoloured this is caused by mains maintenance or change of flow in the network. During these events, iron and manganese levels might exceed these values when sediments and deposits in the pipes are dislodged. It is the iron- and manganese-oxides that give the discoloured water distinctive reddish to blackish tint. This is why we advise not to consume discoloured water, although the concentration of manganese in such water is usually in the same magnitude range as levels found in a pineapple or an English breakfast tea.
Although our manganese levels are substantially lower than NZ’s maximum acceptable value (set based on associated public health risks), they are above the industry aesthetic value threshold of 0.01 – 0.02 mg/L. This is due to the discoloured water incidents in we’ve had in Napier’s reticulation which has occurred more frequently in recent years.
The majority of Napier’s bores produce water with manganese below 0.002 mg/l, however two of Napier city’s bores are in 0.056-0.070 mg/l manganese range and this causes discolouration. NCC keeps these two bores offline whenever possible, however to keep up with summer’s increased demand these are accessed to supply during the hot months. Projects to replace these two bores with low-manganese source are underway.
In order to reduce the risk of illegal water draws from fire hydrants, a dedicated Water Take Station will be commissioned by June 2021. This will allow all registered contractors to draw water without risk of contaminating the main supply.
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