Another 121 properties on the Port Hills are being red-zoned because the risk of further earthquake-triggered rockfalls is too high.
The fate of another 37 properties - six in the Horotane Valley and 31 in Bridle Path Rd - hangs in the balance, with the Canterbury Earthquake Recovery Authority (Cera) not yet prepared to condemn them.
Cera says it will make a decision on whether they go green or red as soon as possible, but it is unwilling to set a deadline as mitigation analysis has not been completed.
"I'm sorry for those remaining property owners that we haven't yet brought the zoning process to a conclusion, but the delay simply shows the degree of rigour being applied to the work being done," Canterbury Earthquake Recovery Minister Gerry Brownlee said.
Today's announcement brings the number of properties zoned red on the Port Hills to 406.
The estimated $250 million cost of buying those properties will be shared between the Government and the Christchurch City Council.
They will split the costs equally of buying properties affected by rockfall, but the Government will pick up the full cost of buying properties affected by cliff collapse.
The council's total estimated liability is $58 million.
Cera chief executive Roger Sutton told The Press the 121 properties zoned red today could not be adequately protected from rockfalls in the event of further quakes.
"We haven't found remediation which fits our criteria," he said.
Exhaustive investigations had failed to find anywhere in the world where rockfall fences were being used to stop rocks from coming down as a result of quakes.
"Rock fences are used all over the place to stop small numbers of rocks that come down as a result of weather events . . . and engineers are really comfortable designing those sorts of fences," he said.
"The issue we have is that rock fences here will have to be designed for lots of rocks coming down . . . and that's much harder for the engineers. We and the engineers started off optimistic that fences could work, but as time has gone on we've become less optimistic.
"I know this will frustrate a lot of people who want protection, but there will be other people who will be pleased by this because they didn't believe protection would work."
Asked whether people living on the border of red-zoned areas should have any concerns about their safety, Sutton said the fact their properties were zoned green indicated authorities believed the life safety risk was acceptable.
"They're probably not as safe as [those] living in St Albans or Linwood, but these people weren't as safe as those in St Albans or Linwood prior to the quake.
"Clearly, these quakes have increased the level of risk.
"They aren't as safe and we can't pretend they are, but we have to give people the facts and they have to make up their own minds," he said.
Brownlee said property owners affected by today's zoning announcement were informed of Cera's decision last night.
He acknowledged some would be disappointed at having to leave their hillside homes.
"While I understand the desire for some people to stay in their homes, we cannot be confident that fences would offer adequate protection should the worst-case scenario of another major earthquake occur," he said.
Today's zoning announcement also sees five white-zoned properties turn green. Those five properties are in Moncks Bay and Flinders Rd, Heathcote Valley.
A decision on whether to green or red-zone eight white-zoned properties in Lucas Ln, Hillsborough, which are potentially at risk from landslides, will not be made until October.
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