EXPLANATION SOUGHT.

Putaruru Press, Volume VII, Issue 305, 12 September 1929, Page 1

EXPLANATION SOUGHT.

5 ARAPUNI TROUBLE. Erosion and Delay. Visit of Power Board Officials. A resume of a recent trip of inspection to the Arapuni power station made in company with the chief engineer, Mr. N. G. McLeod, was given by the chairman of the Thames Valley Power Board, Mr. F. Strange, at last week’s meeting of the board. Soon after the first washout there, said Mr. Strange, the erosion was very rapid. The engineers at Arapuni were faced with a serious proposition. Immediately after the last big falls the Public Works Department had started active preventive measures. The diversion tunnel was being steel-lined for a distance of 50 feet from the valve gates down, so as to take the main stress, which i would be there. Two of the project-

ed penstock tunnels had also been commenced, work continuing day and night. They would take a matter of from four to six months to construct, as the steel for lining them had to come from England. This had been cabled for as a rush order, but the rapid turning out of it was retarded by the number of rivet holes to be bored. If one tunnel could be put through it would take the minimum flow of the Waikato river. It had been suggested that the mouths of the new penstock tunnels should be diverted up-stream, so that the force of water coming through would not tear away the cliff opposite, or interfere with the working lower down. It had also been suggested that to break the full force of the water the tunnel should be rifled, so as to turn the water as much as possible into spray. The question of opening the diversion tunnel was now being seriously considered, so as to drain the J' lake and the water in the headrace to allow cementing to prevent further erosion below the spillway. In opening the tunnel due consideration ’ would be given to Horahora, so as to' : obviate if possible any recurrence of the silting that had occurred last year.

Danger of Vibration. The great danger of using the diversion tunnel was vibration. It was thought that perhaps so great a vibration would be set up that it would, not be safe. There was 801 bof presi sure to the inch, and the water would • go through the tunnel at the rate of 100 ft a second, or, roughly, at a mile a minute. Position Serious. The position was very serious, although not sufficient to warrant anything in the nature of a scare. It •would put Auckland out for some time to come. They would have to go on in the same manner as they had done for the last twelve months. Auckland supply would be adequately met in the summer, but not in the winter. There would be trouble when they arrived at the peak load in the winter.

ed whether it was a fact that after the first slip was reported to Wellington, no action was taken, there beiijg rumours to that effect, Mr. Strange said he was not in a position to state. After the first fall of some 3000 tons had taken place, soon after the commencement, it was naturally to be wondered at why adequate preventive steps were not taken then. It had been originally estimated that it would be a matter of eight years or so for erosion at the falls to work back to the spillway. It was distinctly unfortunate that the department had not provided against a more rapid rate of erosion. Had it taken action then there would probably have been no danger now. Mr. H. M. Corbett thought it was quite evident that the Public Works Department was notified when the first slip occurred. There was no ■use denying that. The responsible officer should be taxed. The success or failure of Arapuni vitally affected the pockets of the board’s district -ratepayers, and the board was entitled to know which departmental officer was to blame for the apparent

j lack of engineering foresight at AraI puni. I The engineer said that although it was easy to be wise after the event, somebody had blundered in not allowing for emergency factors in erosion between the falls and spillway. Mr. Corbett maintained that the first fall of 3000 tons of rock should have been sufficient to warn the Wellington engineers to look out for trouble. An ordinary individual would be on his guard at once. Whole Cause of Trouble. Speaking again, Mr. Strange said that the cause was no doubt due to the breaking down of the first contract. The penstocks should have been ready three years ago. It was hard to understand why, after the first fall, action had not been taken, it seemed to him that when the department realised that it would cost something like £50,000 to £IOO,OOO to make Arapuni safe it decided to “ take tte risk against the show proving a failure.”

Mr. Corbett reiterated that they could not get away from the fact that the action the department was taking now laymen would have taken long ago. “ And yet,” he remarked, “ they are engineers.” Mr. Strange: The engineers do not find the money. They take their instructions from their department.

Mr. Corbett: No; and they throw the responsibility on someone else. Mr. Allen thought that under the circumstances it seemed reasonable for the board to be given an explanation.

Mr. Corbett: I don’t knew who to get to; I’d like to get to somebody. Mr. Strange said he did not think the Arapuni engineers were to blame. They had accomplished wonders in very trying circumstances. There was not the slightest doubt that they would report signs of trouble to 'Wellington, and must have done so., Just how fa.r politics and financial consideration, came into the question, however, it was difficult to say. The position was far from satisfactory, although there was no need for a great deal of pessimism. Finally the board carried Mr. Corbett’s motion, to the effect that the department be asked to detail measures taken for the safety of the headworks, why it was inactive when the first big slip occurred at Arapuni, and to whom the blame was due for failure or negligence to properly safeguard the falls against erosion.