Workers (in picture's right corner) assess the giant slip onto Russell Rd at the top of Helena Bay Hill. Photo: NGĀTIWAI TRUST BOARD / LDR
Up to 20,000 truckloads of clay and debris will potentially need to be removed to clear the giant Helena Bay hill slip.
And authorities are looking at where to dump the up to 100,000 cubic metres of clay, vegetation and debris from the slip.
The slip came down overnight on January 21, after a weekend weather bomb dumped more than a summer's worth of rain on the coast on January 17 and 18.
Photo:
More rain fell on January 21, with the slip coming down overnight to greet the dawn of Thursday, January 22.
Around 100,000 to 200,00 tonnes of heavy wet silt and debris have collapsed in the giant slip.
WDC infrastructure chair Brad Flower said the 50,000 to 100,000 cubic metres of debris that came down across Russell Rd on Helena Bay hill had to go somewhere.
It will mean potentially between 10,000 and 20,000 truckloads of debris may have to be trucked away from the site.
The council estimated it could take up to three months to repair.
Flower said the slip material could not just be pushed over the edge of the site at Russell Rd as had been suggested by some people.
Whangārei District Council infrastructure chairperson Brad Flower says huge amounts of slip repair work are underway. Photo: NZME / LDR
He said that would mean the material would simply go downhill and sediment flowing down into the settlement of Mokau and out to sea.
It also risked creating a dam, which could collapse and flood the tiny community north-east of Whangārei.
Flower said sites for dumping the debris were now being investigated.
These included on local areas where a community wanted to build its whenua above flood height or on suitable farm valleys.
He said the job was not just about what could be seen on the road.
There were big cracks in the land at the top of the slip.
"We might have to go 50 to 100 metres back from the slip," he said of the nature of the repairs at its top side.
Specialist equipment has been brought in to assess the slip.
Flower said there was a huge amount of background planning going in to getting the slip sorted.
"People might think there's nothing going on because they can't see anything happening on the ground.
"But there's a lot of preparation work being done.
This included working with Northland Regional Council on consenting processes.
Whangārei Mayor Ken Couper says the current slip could take eight to 12 weeks to fix.
The last big Helena Bay hill slip in 2007 took six months to clear.
LDR is local body journalism co-funded by RNZ and NZ On Air.
