Council switches to bore water as river supply drops

15 MARCH, 2013

Council is now using a small amount of treated bore water to supplement the main supply to properties in Waikanae, Paraparaumu and Raumati as the big dry continues to bite.

It is the first time bore water has been used since December 2010.

Council staff at the Water Treatment Plant behind Waikanae opened the valve to the bore water system just after 8am today. At this point they are using around 20 litres a second to supplement the main water supply which comes from the Waikanae River.

The water is coming from Bore KB4 which is near the Waikanae Park.

“I doubt whether anyone will notice any difference in the treated water they drink at home,” said David Bassett, Council’s Water and Waste Water Treatment Plants manager. “The dilution rate at 20 litres a second is around 10% which is a very small percentage.”

Mr Bassett emphasised that the bore water went through the same treatment phases as water from the Waikanae River plus two extra steps.

“The two extra steps are at the start of the process where we treat for iron and manganese which appear in higher concentrations in bore water. The bore water is then blended with the river water for further treatment before entering the reticulation system.”

Mr Bassett was confident there would be no problem with calcium build-ups (scaling) of electrical appliances as only a very small amount of bore water was being used.

Council’s trigger for using bore water is when the Waikanae River falls below 1100 litres a second. It is currently running below that figure.

“There is always a balancing act between the river flow and consumption. At present residents are being especially helpful by holding consumption down in line with current water use restrictions. The less water they use, the less blending we have to do.”

It was clear recent publicity about water restrictions was having an impact. “Earlier this week consumption in Waikanae was 6.7 million litres, Paraparaumu 10.5 million litres, Ōtaki 4.2 million litres and Paekākāriki 0.86 million litres.

Following significant publicity, the figures dropped to 6.5 million litres in Waikanae, 10 million litres in Paraparaumu, 4 million in Ōtaki and 0.78 million in Paekākāriki.

“Clearly people are heeding the warnings and helping out by cutting back on their water use.”

Mr Bassett said the use of bore water would stop as soon as significant rain fell in the headwaters of the Waikanae River.

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