Dangling boulder 'Rocky' blown up during Kaikoura road closure

The closure of State Highway 1 either side of Kaikoura due to slips caused by Cyclone Gita was a silver lining for engineers, allowing them to blow up a massive boulder that has been dangling over the road. 

The North Canterbury Transport Infrastructure Recovery (NCTIR) captured the moment 'Rocky' was blown up on camera.

The footage shows NCTIR's geotechnical team blowing up the 700-tonne boulder about halfway up the centre of the hill face, just north of Kaikoura near Ohau Stream. 

NCTIR health and safety manager Stephen Bell says generally a helicopter wouldn't fly so close to the rock face, but this was the safest way to deliver explosives to the site.

Rocky is believed to have been first exposed in the 2016 earthquake, and the closure of SH1 was the perfect opportunity to get rid of it. 

Preparation started in November last year, when the team began drilling holes into Rocky.

"Ninety-two drilled holes were loaded with a combined total of 32kg of explosives, and there was a slight sequence delay," said engineering geologist Frances Neeson.

"The controlled blast was extremely successful," Mr Bell said. 

The road was reopened on Friday. The New Zealand Transport Agency advises motorists travelling on SH1 south of Kaikoura there will be delays.