Redclyffe substation in Hawke’s Bay set to be rebuilt at same site, but 1.7 metres higher, after Cyclone Gabrielle flooding

Transpower has revealed its preferred option to rebuild the Redclyffe substation on the same site where it was flooded during Cyclone Gabrielle.

More than 90,000 homes in Hawke’s Bay lost power after waters more than 1.5 metres in height washed through the substation’s control room during the cyclone.

It took four days before some of the supply was restored in Napier, but it was more than a month before the lights came back on for other locations on the network due to local supply issues such as fallen lines and poles.

Transpower and Unison announced on Thursday that strengthening and improving the Redclyffe substation at its current location was the preferred way forward for both, rather than moving it to a new location.

Detail from an aerial shot of the flooded Redclyffe substation. Photo / Supplied

The rebuild will be covered through power bills and at this stage is expected to cost each Hawke’s Bay power consumer an average of $400 over a 40-year period.

Transpower estimates it will cost up to $35 million to rebuild the substation in the same location and said the approach would deliver significantly increased resilience for the region within two to three years.

Building a new substation elsewhere could take 10 years and cost over $200 million while being unlikely to provide additional resilience compared to rebuilding at the existing site.

Mark Ryall, Transpower executive general manager of grid delivery, said modern design standards and new engineering and technology approaches would give the site one-in-450-year flood protection.

Transpower plans to build new high-voltage equipment and raise the ground level of the substation to protect it from similar weather events.

Ryall said flood modelling indicated the critical parts of the site would need to be raised by about 1.7 metres, which gave leeway above the minimum level to account for climate change too.

“Already, as we’ve recovered the site, we’ve made it more resilient. We’ve lifted a lot of the computer systems or the brains of the site up above the existing water level. We also have some existing planned work underway which we will continue to roll out to get to that resilience level so a flood event like Gabrielle would have less impact today,” Ryall said.

He pointed to Transpower’s Wairau Rd substation in Auckland, built to a modern design standard in 2013, which had 1.5 metres of water through it but stayed fully operational during the Auckland Anniversary floods.

Community consultation on the proposal would take place in the middle of the year and take a few months to complete.

Crucial parts of Redclyffe substation will be raised about 1.7 metres in the preferred proposal, giving the site resilience against a one-in-450-year flood. Photo / Warren Buckland

Jason Larkin, Unison Networks general manager commercial and regulation, said Unison and Transpower have engaged with local stakeholders to better understand the region’s long-term electricity needs.

Those stakeholders include some of the region’s largest power users, key infrastructure and interest groups including Napier Port, Hawke’s Bay Airport, mana whenua groups and the Regional Recovery Agency.

“We’ve been through a robust exercise which highlights this is the right location,” Larkin said.

“Through that process, we’ve had good feedback around community concerns... questions around different options, but ultimately I think support for the process we have been through.”

As Transpower is a state-owned and regulated entity, Ryall said the rebuild cost would be recovered through power bills.

The flooded Redclyffe substation. Photo / Supplied

Larkin said each power consumer in Hawke’s Bay would contribute about $10 annually over 40 years to the rebuild cost.

Transpower will provide more detail on the planned improvements once consultation with the community on the preferred plan begins and concept plans will be released to the public “in the next few months” according to Ryall.

James Pocock joined Hawke’s Bay Today in 2021 and writes breaking news and features, with a focus on the environment, local government and post-cyclone issues in the region. He has a keen interest in finding the bigger picture in research and making it more accessible to audiences. He lives in Napier. james.pocock@nzme.co.nz