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Key FactsNgā meka whai tikanga

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.

Key Facts

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.

Supply Areas

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.

Consumption

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.

DetailsAmount
 Total Annual Consumption  10,032,280m³
 Average Daily Consumption  27,486m³ 
 Peak Day Consumption  39,408m³
 Minimum Day Consumption  16,045m³

Source of Water

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).  

Pump Stations

There are eight booster pump stations servicing the City with a total of 25 pumps.

Reticulation

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.

Storage

  • Ten reservoirs at seven different locations provide approximately 29,757m3 of storage. Enfield reservoir on Hospital Hill, Thompson reservoirs on Bluff Hill and Taradale 1 reservoir are our major reservoirs. We've recently constructed a second reservoir next to the existing Taradale 1 reservoir which has a capacity of 9,200m³. There have been some delays due to construction faults: we anticipate this reservoir will come online in early 2019.  
  • Three small reticulation systems provide water to residents on the hills of Taradale. These systems have small reservoirs and use booster pumps to pump water from the Taradale bores. 
  • Two reservoirs serve the Bay View area. Water is supplied to Bay View using a couple of booster pump stations that draw water from the Napier water supply system.

Water Quality

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:

  • Hardness - the sum of all calcium and magnesium compound in water results in the total hardness, measured in milligrams calcium carbonate per litre (CaCO3 mg/l). Average total hardness value for Napier water is 66 mg/l, which equals to 6.6 French degrees or 3.7 German Degrees. American Water Works Association classifies waters with up to 75 mg/l CaCO3 as soft water.
  • Alkalinity – is the capacity of water to resist acidification. Napier water’s alkalinity is in range 59 – 82 mg/L CaCO3, depending on the source used.
  • pH – the pH of water is a measure of the acid-base equilibrium and, in most natural waters, is controlled by the carbon dioxide-bicarbonate-carbonate equilibrium system. An increased carbon dioxide concentration will therefore lower pH, whereas a decrease will cause it to rise. The pH of most drinking-water lies within the range 6.5-8.5. Water in limestone areas such as within aquifer beneath Napier tend to have a higher pH value. Average pH of Napier reticulated water sits around 8.1.
  • Total Dissolved Solids (TDS) – is a measure of the dissolved combined content of all inorganic and organic substances present. Mean TDS value in Napier reticulation is 96 mg/l.
  • Nitrates – Nitrate is one of the most frequent groundwater pollutants in rural areas. The origin of nitrate is primarily from fertilizers, septic systems and manure storage or spreading operations. The Maximum Acceptable Value (MAV) in Drinking-water Standards for NZ is 11.3 mg/l, expressed as Nitrate-N. Nitrate-N levels vary across Napier bores and are in range <0.01 – 0.18 mg/l.
  • Heavy metals – None of the heavy metal elements tested in our groundwater (including chromium, cadmium, mercury, lead, cobalt, nickel, copper and zinc) has ever returned above 50% of the Maximum Acceptable Value.
  • Sodium, Potassium, Calcium, Magnesium and Chloride – average values in Napier reticulation for these ions are 11.4 mg/l, 1.5 mg/l, 22.0 mg/l, 2.0 mg/l and 8.1 mg/l respectively.
  • Iron and Manganese – The National Drinking Water Standards set a guideline value for iron at 0.2 mg/l. Average iron concentration in Napier supply is 0.02 mg/l. The maximum acceptable value for manganese is 0.4 mg/l. Average manganese concentration in Napier supply is 0.02 mg/l.

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.

 

 

Water Take Station

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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