THE HYDRO WORKS.

Taranaki Daily News, 30 April 1923, Page 4

THE HYDRO WORKS.

FLAWS IN NO. 2 TUNNEL. CAUSE NOT DEFINITELY KNOWN. “There are three or four possible causes of the cracking of the lining of the tunnel, but which one is actually responsible we won’t know until we have investigated the «eat of the trouble,” said Mr. Blair Mason on Saturday to the Mayor (Mr. F. E. Wilson) and several members of the incoming council who paid a visit to the hydroelectric works at Mangorei to obtain at first hand a knowledge of the extent of the flaws which have developed in No. 2 tunnel. This tunnel is the one which leads into the huge forebay, ox* surge chamber, which is visible from tin main road. The flaws became apparenc after the water had been turned into the tunnel on Sunday week in readiness for a test of tho pipes which ran from the forebay to the power house. The visitors on Saturday comprised the Mayor, Messrs. J. Kibby, R. A. Large, V. Griffiths, S. G. Smith, M.P., and F. A. Amoore, with the borough manager (Mr. F. T. Bellringer) and representatives of the Press. They were met at the works by Mr. Blair Mason (consulting engineer) and Mr. R. Peerless (resident engineer). Passing through the forebay, the party walked through the ferro-concrete “pipe” until they reached the point in the tunnel where the ferro-concrete ends and th? “lining” commences. The tunnel, it may be mentioned, is ferro-concreted at each end so a« to withstand the pressure of the water. In the centre it is merely lined with six inches of concreta to reduce friction, the volume of eartli above being considered sufficient to withstand the water pressure. This lining is not intended to carry the weight of the earth above. For a distance of about 150 feet from where the ferroconcrete terminates at the forebay end, a crack is visible in the floor, commencing at the bottom of one side of ths tunnel and gradually edging over unti. it terminates against the other side. Other cracks are visible, and a few inches of plaster have fallen away. As a remedy fox - the trouble in the tunnel, Mr. Blair Mason, in reply to a question, suggested turning the damaged length into a ferro-concrete pipe of sufficient strength in itself to withstand the water pressure. However, a full report on the damage, causes an 1 effects, and remedy is being prepare! and will be presented to the council in due course. The effect of the breakdown will mean a delay in the turningon of the water for about a couple of months.