Dannevirke’s troubled dam: More leaks found

The tears found were expected to be a contributing factor to ongoing leaks in Dannevirke's dam. Photo / Paul Taylor

Those working on Dannevirke’s dam have found further leaks and planning for repairs was under way, but Tararua District Council is not anticipating any water restrictions.

Group manager of infrastructure Chris Chapman said the leaks were found on May 5.

Two tears, near the base of the western dam embankment, were found during examinations with remotely operated underwater vehicles (ROV).

Tararua District Council group manager of infrastructure Chris Chapman.

Chapman said they could not be certain whether those were the only tears in the liner, but it was expected the tears had been contributing significantly to the ongoing leakage, of around 20 litres per second, that had previously been communicated and reported.

He reiterated these were not new leaks, but part of the ongoing issues which were first identified nearly two years ago.

“We know there has been leakage from the impounded supply, but unfortunately, previous attempts to locate where it’s coming from haven’t identified the tears found on May 5.”

A New Plymouth company, New Plymouth Underwater, had been commissioned by the council to complete further inspections with the aim of locating possible leakage points and finding possible further deterioration.

When asked why a local company hadn’t been commissioned, Chapman said he wasn’t aware of any specialist people or companies within the Tararua District that could carry out the inspections, which would be underwater and in complete darkness, but he would welcome recommendations.

Planning for temporary repairs was already under way and was expected to be finalised by Friday.

A council spokesman said New Plymouth Underwater would develop a specialised plan for divers to make temporary repairs once that was done.

During that stage, water would be drawn directly from the Tamaki River and not the dam, and the river water would undergo the same treatment process to provide safe drinking water.

Works were set to be conducted in the first week of June and water restrictions were not anticipated.

Meanwhile, Chapman said options for permanent repairs of the dam were still being investigated and assessed, including with council stakeholders so they understood the cultural, environmental and regulatory impacts of the options.

“This also includes options for how we continue to provide safe, reliable water to Dannevirke while permanent repairs are undertaken.”

He said if the impounded supply was turned off while the permanent repairs were undertaken, there would be “significant disruption” to Dannevirke’s water, including the likelihood of boil water notices and water shortages.

“The options being assessed include ways to minimise the impacts.”

A report was expected to be provided to the council’s elected members before the end of June.

“I believe we will then be engaging with the community.”

The council will also be providing regular updates on social media and via its website.