Ruapehu District Council (RDC) is preparing to return the water source for Raetihi to the Makotuku River which was contaminated by a diesel spill in October last year.

The spill from a faulty tank supplying the Turoa ski field on Mt Ruapehu leaked 19,000 litres of diesel into the Makotuku River forcing RDC to switch the water source for Raetihi township to the Makara Stream.

A major multi-agency civil defence response effort was required in response to the spill including the provision of emergency drinking water supplies for two weeks while Raetihi was without potable reticulated (tap) water.

RDC Chief Executive, Peter Till, said that Horizons Regional Council (Horizons) which has had responsibility for cleaning-up the diesel spill in the Makotuku River has advised that it has decontaminated as much of the river as possible.

“Horizons states that there is still some diesel contamination trapped within the scree slopes on Mt Ruapehu that has been deemed to be impractical to recover,” he said.

“There is a risk that some of the trapped diesel finds its way into the Makotuku during significant rain events.”

Mr Till said that to manage this issue RDC has installed a hydrocarbon sensor on the raw water line from the Makotuku River feeding the Raetihi water treatment plant settling ponds.

“The diesel sensor is incredibly sensitive and during testing has been able to detect less than one fifth of a teaspoon of diesel in 20 litres of water.”

“When diesel is detected by the hydrocarbon sensor the raw water line is automatically shut-off to prevent any contaminated water entering the settling ponds and an alarm is sent to an on-call operator.”

“The settling ponds and tank hold a day’s worth of water usage and council is able to switch back to the Makara Stream as a raw water source within hours ensuring water supply to the township is not affected,” he said.

“Testing of the hydrocarbon sensor and other new systems installed since the diesel contamination have been very encouraging.”

“However before we switch back to the Makotuku River as a raw water source we want to test the sensor during more adverse weather conditions than we have had lately.”

Mr Till said that council hoped to be able to advise a target date for the switch back to the Makotuku at the next Waimarino Waiouru Community Board meeting on Thursday 13th February.

“Before the switch over council is planning a public meeting and open day to allow the Raetihi community to see the new systems first hand and ask any questions they may have,” he said.

Mr Till noted that despite the investments and upgrades made to Raetihi’s water treatment plant and reticulated network since the diesel contamination there are still significant outstanding issues.

“It needs to be recognised that this is only a medium term solution at best,” he said.

“Over summer council staff have been preparing for a meeting to discuss alternative water sources for Raetihi.”

“Major components of the Raetihi water treatment plant and reticulated network are coming to the end of their predicted useful life.”

“For example the raw water line from the Tohonga Junction to the Raetihi Reservoir which suffered two breaks in a week this month is estimated to cost around $2 million dollars to replace along its current route.”

“Ohakune’s water treatment plant has similar issues with aging plant and as such all Waimarino communities will shortly need to start working alongside council to investigate long term options for their potable water.”

ENDS

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