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Port Hills still dangerous - engineer

Thursday 31 Jan 2013 4:46 p.m.

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A senior geotechnical engineer says rock falls in Christchurch’s Port Hills will happen again, and could kill more people.

Nearly two years on from the February 2011 quake, CERA’s chief geotechnical engineer Jan Kupec says the risk is still very real.

One affected property has a great view of Christchurch but no one's been able to enjoy it since the temblor because it is perched on the edge of a cliff overlooking Sumner Beach.

But Mr Kupec says there are plenty of other less obvious dangers lurking in the Port Hills.

Last week a 40-tonne boulder crashed through an abandoned house in Sumner. Mr Kupec says it’s just one of hundreds that were made unstable by the quakes.

“Even without any aftershocks, the rocks, like in 31 Finsarby Ave, will still be able to be dislodged by natural processes like erosion shrinkage, by heat expansion and so on and so forth, and that process will continue.”

The next biggest challenge facing authorities in the Port Hills will be demolishing hundreds of red-zoned houses at risk from cliff collapse or rock fall.

CERA Port Hills manager Brenden Winder says safety measures for workers will be needed.

“Potentially there'll be sites where a safe refuge is required to be on site before the work continues. The use of heavy machinery will have to be carefully considered, how many people on site [and] access to the site.”

Mr Winder says all those extra safety precautions mean the houses could take up to three years to remove.

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