Blasting a crater channel seen as practical option

Ruapehu Bulletin, 24 June 1997, Page 1

Blasting a crater channel seen as practical option

Blasting a channel with explosives would be a much simpler and cheaper way to deal with the volcanic debris dam at Ruapehu's Crater Lake outlet. That was the suggestion of an engineering contractor the Bulletin spoke to last week. Following the announcement from the Minister of Conservation, Nick Smith', we contacted a number of local contractors to try to get a feel for the practicalities of cutting a 90m trench, five metres deep, and 5-10 metres wide, 2400 metres up a volcano. "Why not just use a few sticks of gelignite," said one engineer we spoke to, who did not wish to be named. He said explosives were used extensively on the mountain already, to control avalanche hazardand to clear boulders from ski runs. Also,

the mountain. does "a fair amount of its own exploding", he understated. The engineer conceded that the area was sacred to local Maori and such an approach may not be appropriate, but looking at it from a purely practical point of view, that was the best solution. He said one man flown up to the crater with a portable generator could easily drill the necessary holes and carry out the blasting. If an excavator was used, it was likely that they would have to use explosives anyway, as this was the usual method for shifting large obstructions. He estimated the cost of blasting the trench at about $20,000, while using a 30-tonne excavator would be $40,000-$80,000, given the problems of getting to the site and working on the volcano.