Rockfall-threatened Port Hills red-zoners can "make themselves green" by convincing the Christchurch City Council to lift notices barring access to their homes, the Earthquake Recovery Minister says.

Gerry Brownlee yesterday announced the details of Port Hills land zoning reviews, which would look at the boundaries used to identify residential red and green zones.

The review will not cover council-issued section 124 notices, which barred entry to homes because of rock fall or landslip risk, or individual options to mitigate that danger.

Brownlee said mitigation would not be considered in the review because it had been deemed ineffective in the original zoning decisions.

Life-risk in red-zoned areas was unlikely to return to above the acceptable 1 in 10,000 level in the "foreseeable future", he said.

"Some people are arguing that if mitigation was put in place, then they'd be that 1 in 10,000 zone. We weren't persuaded that it was something that could be done with any particular ease, in a timely fashion or at a reasonable cost.

"The vast majority have accepted that and are moving on and, quite frankly, many of them are very grateful to do so."

Brownlee would not be drawn on why red-zoned properties could not be re-zoned green if their risk was mitigated.

"We're talking very hypothetically here and that's something I really don't want to get into because I'm not an engineer.

"If people are able to convince the council that the mitigation work they're going to put in on their property will protect them and change their life-risk factor, they can stay there. By definition they make themselves green."

Mayor Bob Parker said while it was unlikely the life-risk in red-zoned areas would fall within acceptable levels in the short term, individual mitigation measures would be seriously considered.

"There will be, potentially, properties on which somebody might be able to propose a [successful] mitigation measure. That of course is going to require some very comprehensive standards and engineering resources and they're going to need to show they can meet all the dangers that authorities believe they are potentially subject to."

The council was unlikely to undertake remediation work, Parker said.

"It still comes down in the end to the cold, hard reality of a cost-benefit analysis. When the cost of providing protection for a house or a group of homes exceeds the collective value of those properties, then it's very difficult to mount an economic argument that council should do something the Government has already turned down."

Property owners have until October 26 to apply for a review, with the exception of eight Lucas Lane property owners still to be zoned.

The zoning review panel will be chaired by Keith Turner and include Canterbury Earthquake Recovery Authority and council representatives and an independent geotechnical engineer.

The review will be completed in December.

Those seeking a review should email info@cera.govt.nz or call 0800 RING CERA.

- © Fairfax NZ News

Comments