WATER FALLING

Dominion, Volume 25, Issue 278, 19 August 1932, Page 12

WATER FALLING

Arapuni Coffer Dam DROP OF 9 INCHES Engineer’s Hopeful View Dominion Special Service. Auckland, August 18. A fall of nine inches in the level of the water in the coffer dam constructed in the headrace at Arapuni was noted this morning, compared with yesterday’s level. There has been no pumping during the last three days, and the reduction in the water level is due to the fact that the process of making the walls of the dam watertight is becoming effective and to the fact that the water in the dam is making its way through the system of drainage channels provided above the power-house. Referring to-day to the time occupied in unwatering the area with the coffer dam, Mr T. Rabone, engineer-in-charge, stated tliat the dam was built in a race in which water was rushing past at the rate of from 3000 to 4000 cubic feet per second, or seven knots. The height of the sandbag walls was 12ft., and It was not reasonable in the circumstances to expect such a structure to be immediately watertight. Now that the water level in the dam was falling, Mr. Rabone said he was quite confident that the leakage could be controlled. As soon as the water level in the coffer dam was sufficiently low the work of repairing that portion of the headrace lining which had sagged would be put in hand. Repair equipment and material were on the site. No pumping was done to-day the diver and other workmen being engaged bn caulking the walls of the dam. Boring Is still In progress on the eastern bank of the headrace near the cut-off wall for the purpose of investigating the possible sources of the leakage. The headrace is more than half filled with water and the turbines in the power house are still running at slightly reduced pressure. The installation of the second system of gates in the diversion tunnel has been suspended on account of the fact that water is passing through the tunnel. The existing gate has been closed twice since the discovery of the leak in the headrace a fortnight ago, and when the last examination was made yesterday no evidence of erosion was found, and the condition of the tunnel and gate was satisfactory.