Council Has Plan for Improving Ōpunakē Water Supply

Council CE Waid Crockett apologised to residents on the Ōpunakē water supply for the discoloured water many experienced over the weekend and says the Council has a $3 million programme in place to improve the town supply.

“I’m very sorry for the incident, it was unacceptable and frustrating, “says Crockett. “We know there are issues with periodic discolouration of water and have set aside $3.3 million in our 2021-31 Long Term Plan to upgrade the plant, improve the taste, odour and discolouration issues, increase storage and improve the supply,” he says.

Crockett says the Council are investigating what caused the recent discolouration, which occurred after a period of cool wet weather on the mountain, a period that typically means there is release of metals in the river water.

Background

The discolouration happens because of where Ōpunakē’s water is sourced. The head waters of the Waiaua Stream are high up in the exposed scree slopes of Maunga Taranaki/Mount Taranaki which experiences frequent erosion and flooding. The material from the mountain also carries a lot of naturally occurring iron and manganese which flows down to the catchment, where the Council takes the water for treatment. In a dissolved form these metals tend to pass through the existing treatment process, that has a clarifier, membrane filters and then the water is treated with chlorine, which ensures it is safe to drink. These dissolved metals are oxidised by the chlorine disinfectant that occurs at the end of the process. Once oxidised, the metals accumulate in tanks and reservoir before water passes to consumers. These metals are not always fully captured during periods of high water use and can be carried into the piped network and then build up on the inside of the pipes to create a film as water runs through the network. When there are flow changes within the pipes the films can dislodge to cause discoloration, along with fine particles which may sometimes be noticed.

What have we been doing:

Earlier this year, Council completed a $420,000 upgrade of the water treatment plant to reduce the amount of sand accumulating in the intake. This was done to restore damage caused by several floods that have occurred since mid-2021.

What is the Council doing now:

Our contractors are conducting localised flushing to remove discoloured water from the network this week. We are also increasing the amount of monitoring of water clarity in the network - with weekly samples taken at the bottom of the trunk main and in areas where the colour of the water is the worst.

Over the last three years, we have also conducted a town-wide flush of the network in September. As a result of what happened in the weekend, we are bringing that scheduled work forward and it will be started before the end of this month.

What we have planned:

As part of our 2021-31 Long Term Plan, there are several projects planned for the Ōpunakē Water Supply including:

• $600,000 has been budgeted to improve the treatment process in the 2022/23 financial year. Preliminary engineering options analysis has been completed and the design is currently underway for this.
• An additional $1.9 million reservoir has been budgeted for the 2023/24 financial year. Preliminary engineering design is currently underway.
• Over $750,000 has been budgeted to resolve the brown water issues in 2027/28, however we will be asking Council to bring this work forward
• A plan is also being developed for the replacement of parts of the reticulation network.

“Due to the nature and complexity of where we source Opunake’s water it is not going to be an immediate fix,” says Crockett. “However, we have a plan in place and while we are waiting for this work to be completed, we will increase the amount of water quality monitoring within the network and the frequency of the town-wide flushing to minimise the effects. In the meantime, if you do continue to experience discolouration, please call us on 0800 111 323 and we will arrange flushing to clear the pipes.”