THE ARAPUNI SCHEME.

Otago Witness, Issue 3775, 20 July 1926, Page 34

THE ARAPUNI SCHEME.

AUCKLAND, July 18. The Arapuni hydro-electric scheme entered on a new phase yesterday, when a portion of the intake dumpling was removed by explosives, which turned a portion of the river into the diversion tunnel and outlet. The dumpling was completely removed by the explosion of over a ton of blasting gelatine. The chief problem had been the removal of the outlet carrier without causing the displacement of the hanging country. The method adopted was to lay the charges in perpendicular pipes going down to an average depth of 20ft. There were 64 of these, and the explosives they contained were equivalent to a little over lib per cubic yard. < The intake charges were laid in horizontal bores and were designed to remove 6ft from the top of the lip. The clay was broken but not displaced by the explosion, and a gang of men was put on to open the channels, which quickly scoured. The tunnel was full in an hour, when the second explosion, composed of 64 mines, fired simultaneously, was set off. This was most spectacular, the debris rising 500 ft. It successfully made a clear canal of running water. By the time the smoke cleared there was no dislodgment of any moment of the adjoining country.