Council's rockfall report 'whitewash' say red-zoners

20:17, May 07 2014

Port Hills red-zoners are urging city councillors to reject a "whitewash" report dismissing area-wide rockfall protection.

A new report being tabled at today's council meeting says the small number of properties that would benefit, coupled with the high costs of such area-wide mitigation work, makes it an "unattractive and largely unaffordable" option.

It identified just two properties in Avoca Valley, two properties in Morgans Valley, 13 properties in the Bridle Path Rd area, and seven properties in the hills above Sumner that could potentially benefit from area-wide mitigation work.

Sumner red-zone resident Phil Elmey said the report contained "very scant specifics" about the cost and design of the structures it had considered.

Council staff had "cherry-picked" areas to analyse, which he believed was not what Mayor Lianne Dalziel had intended when she sought an investigation.

"Nothing [in the report] suggests this is anything but a whitewash," Elmey said.


"Our expectations were that the council were going to follow the mayor's instructions and show to her area-wide mitigation - the whole of Morgans Valley, the whole eastern side of Sumner and the whole of Sumner-Wakefield."

His message to the council today would be: "This is your problem to fix, not ours".

Andrew Abakhan was disappointed his largely red-zoned Sumner street had not been considered in the report, given the council already owned the land above it. His was the only affected property not already owned by the Crown, but it was still a "terrible waste" to demolish up to 25 homes that could be protected.

Port Hills MP Ruth Dyson said councillors should reject the "disappointing" report, which she had expected to be released in February.

"I think the significant delay in the report and the quality of it would cause me, if I was sitting around the council table, to just demand better," she said.

"Chief planning officer Michael Theelen said the costs were based on "historical quotes, estimates or actual costs" and included allowances for contingency, access costs, supervision, consents and property purchase. The bunds in the report were based on designs that used wire mesh units and compacted fill. The rockfall catch fences consisted of posts, cables, mesh and anchorages that absorbed energy when struck.

"We do not prescribe the actual design of these, which are left to the consultant, but for the purposes of our work we have used industry standard designs," Theelen said.

In 2012, The Press reported that a study for the Canterbury Earthquake Recovery Authority by geotechnical firm Geovert found area-wide rockfall protection was "realistic and achievable", but the Government ruled the option out because of cost and the risk that fences could be breached by rock strikes.

New Zealand geotechnical firm Maccaferri also released a report which found mitigation was practical and viable.

The Press