DON SCOTT/Fairfax NZ
BETWEEN A ROCK AND A . . . Avoca Valley homeowner Warren Batchelor and his five-year-old daughter Erica with the collection of rocks that landed on their property after the February 2011 earthquake.
JOHN KIRK-ANDERSON/Fairfax NZ
THE NEIGHBOURS: Tony Ging, with his son, Lewis, 3, whose Avoca Valley home was zoned red on Friday.
A Christchurch man is calling for the immediate release of rockfall data after his home was given the all-clear despite rocks smashing a tractor in half just metres from his door.
Warren Batchelor's Avoca Valley Rd property was zoned green in June, having been red-stickered because of the risk of rockfall after last February's earthquake.
His family returned home about three weeks ago despite several near-misses in the quake, including a boulder that was stopped near to his house by a now written-off tractor.
However, Batchelor has questioned data used after neighbours with fewer fallen rocks were zoned red on Friday.
"We're green with a pile of rocks. Over there [at the neighbour's], they're red with no rocks," he said. "The hill slopes are comparable, so we don't understand why no rocks is red and a lot of rocks is green."
There were no concerns about the zoning in June because most of the neighbours were still white.
"Now everyone of each side of us is red, we have a reference point that doesn't make sense. With the lack of any supporting information, it makes it difficult for us to judge."
Batchelor wanted the data used released to verify whether the assessment was accurate.
The Canterbury Earthquake Recovery Authority said on Friday information would not be released until all zoning decisions were finalised, which was expected to be October.
"We want some transparency and some sane decision-making," Batchelor said.
"Our concern is, without any substantiation of our green, we don't whether we're safe living here. The only data we've got is a pile of rocks which is bigger than everybody else's."
Computer modelling and rock mapping was used to determine the "life risk" formula.
Cera chief geotechnical engineer Jan Kupec said in June the risk of death in some areas was between one in 100 to one in 1000.
Batchelor's neighbour Tony Ging, who was zoned red on Friday, said his rockfall experience created doubts about the modelling results.
Official Information Act requests for the data to be released this month were declined.
"You can peer-review things as much as you like from the comfort of your desk, and the virtual models might be robust in themselves, but are there considerations that haven't been put into those models from actually coming and looking reality?" Ging said.
The life-risk band for his property was between 1 in 1000 and 1 in 5000.
"Are we 1 in 4999 or are we 1 in 1001? How close are we?
"I desperately want to move back to my property but I want to know it's safe."
Ging questioned why protective fencing or bunds could not be used.
Cera chief excutive Roger Sutton said last month red-zoned areas had "vast concentrations" of rocks, which meant the options were unlikely to work or not be cost-effective.
Ging said the land he and another red-zoned neighbour owned had a combined valued of more than $1 million.
"I'm open to putting a rock bund behind the house if need be, but that doesn't even seem to be a consideration," he said.
"You could put a bloody big pile of dirt in place for that [$1m]."