A major Alpine Fault rupture could leave communities in the Mackenzie District isolated, with councillors warning Tekapo could be split in two and cut off from critical emergency responders.
By Claire Taylor of Local Democracy Reporting
Mackenzie District Council emergency management officer Nils Walzel presented a report to the council meeting last month, where he discussed new emergency response plans and district readiness.
Councillors discussed the impact of an Alpine Fault rupture on the district, particularly with the Ostler fault zone running directly through it.
The Ostler Fault sits east of the Alpine Fault, running about 65km from the Ben Ohau Range north of Twizel to the Ahuriri River in the Waitaki District.
Councillor Jan Spriggs questioned what would happen if the district’s leaders were cut off from leading the emergency response.
"I think it would be really useful as a councillor who may actually be isolated ... if there was some understanding of what might happen in that situation," Spriggs said.
"Communication's going to be down, bridges are probably going to go."
A major Alpine Fault event would leave councils largely responsible for managing their own response and communities, council chief executive Angela Oosthuizen said.
If a magnitude 8 earthquake on the Alpine Fault goes, just about every council will be "on their own", she said.
"So the message we should be sending to our communities is 'you should be able to get through for at least a week with food and water'," she said.
"We’ve got to be prepared at the local level."
Walzel said the emergency team was introducing additional operational checks of the district’s three generators in Fairlie, Tekapo and Twizel to ensure there was appropriate oversight and fuel management going forward.
"We just want to [make] sure that there’s operational oversight and a good fuel management plan," he said.
'Infrastructure on one side and a generator on the other'
Councillor Mark Adams questioned whether a permanent trailer generator could be installed at the Twizel Events Centre, the district’s designated welfare centre.
Adams said the centre was not sufficiently earthquake strengthened for an emergency management facility.
"Our infrastructure is not necessarily as earthquake strengthened… as one would wish for an emergency management facility."
Adams also questioned whether the Tekapo Community Hall was a suitable location for the town’s generator in an earthquake event.
"The hall hasn’t had high earthquake strengthening either, so... I think there might be an impact," he said.
He questioned whether the generator could be moved to a more suitable location.
The recycling park appeared to be out of the way in an earthquake, he said.
"It’s quite feasible that Tekapo gets split into two, and you could end up with infrastructure on one side and a generator on the other."
Walzel said other locations would be considered, but the resource park had the systems needed to support the generator.
"There’s a facility to keep it under a roof... there is a solar arrangement to keep the start-up battery constantly powered, so that its always ready to be used," he said.
Adams also questioned the resilience of key sewerage pumps during an earthquake.
Operations and regulatory general manager Neil Jorgensen said backup systems were in place and the water team was working to improve resilience.
"We have our own backup systems to enable systems to operate... that does have a generator plug, and our guys will go out and plug that in if required during an event."
Running from Milford Sound to the north of Lewis Pass, the Alpine Fault has a 75% chance of rupturing in the next 50 years, according to the AF8 website.
The site estimated an 82% probability the quake would exceed magnitude 8.0, releasing 250 times more energy than the 2011 Christchurch earthquake.
Records showed 27 ruptures in the last 8000 years, averaging every 300 years, with the most recent in 1717.
– LDR is local body journalism co-funded by RNZ and NZ on Air
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