THE MANGAHAO WORKS

Dominion, Volume 16, Issue 172, 9 April 1923, Page 8

THE MANGAHAO WORKS

MR. MITCHELL HAS HIS DOUBTS

“NEVER A FIRST-CLASS SCHEME”

Mr. G. Mitchell, secretary of the ■Central Progress League, reports as follows on his latest visit to the hydroelectric works at Mangahao :— “I visited Mangahao on Monday, March 26, and went right down to the head works at Mangahao. As my last visit was on January 10, one naturally looked forward to seeing a decided advance in the progress of the work, but so far as the dams—■which are the key works —are concerned, such anticipation was not realised. “The men engaged number 406, and progress has been made with the power-house, the pipe line, and surge chamber. Tho first poles have been erected fur the Shannon-Bunnythorpe transmission line, and only nine chains of No. 2 tunnel have yet to be pierced. But all these works are now subsidiary to the huge dams, which works have long been tho pivot of importance. It is unfortunate that tho work on the dams was not pushed on earlier, as the constant danger of flcods will always bo liable to cause toss and delay.

“Tho completion of the works will now governed b.y the completion of tho dams, and they are little further advanced than they were nearly two months ago. There arc two reasons for this. Firstly, the fact that two big floods have occurred and washed away some of tho structures and works at Mangahao dam, which will delay the work for two or three months. Secondly, continuous trouble has been met with in the foundations- It was first considered that the dams would butt on to th© rock faces showing at Mangahao, but on the south side this face proved to he a ledge only, and a long deep excavation, right up to the base of the hill, had to be made before rock was reached. “Tho difficulty at Mangahao dam is over, and concreting should start within a month’s time, but difficulties may have to be overcome in the bed of the river before any conjecture of the time of completion could be made. “At Aripeti dam. where it was thought to be all plain sailing, the hill on the north side has proved to bo of shingle composition for a great depth. It is anticipated that from these two causes the work will be delayed six months. “Mangahao could never be considered a first-class scheme. It necessitated difficult tunnelling, and big dam construction on ground which has proved very unsatisfactory, causing extensive excavations before a foundation could bo found; in fact, furthei exploring and. excavations must yet bo made before the foundations for tho Aripeti dam can be completed. Tho nature of the ground and foundations for the dams do not seem to have been properly explored and tested before th© scheme was decided on. Had proper tests been made, in the light of experience it is quite a moot point if Mangahao would ever have been start“Now the progress of the work on the dams is preceded by constant exploring for foundations.. The ground is eo uncertain that neither the time nor the cost of this work can be ascertained with any degree of certainty. Mr Parry’s estimate was nearly £500,000, but the ultimate cost will bp nearer double this amount, and the original three years’ estimate Ct time to do the job will overlap five st “[ S can only again emphasise the necessity of concentrating all possible energy on the dams, and with decent weather and no disasters there seems little reason even now why the worK should bo much into next year before power is turned on.”