FLOOD-FIGHTERS BEGIN DAM IN CANYON

Evening Post, Volume CVI, Issue 107, 2 November 1923, Page 7

FLOOD-FIGHTERS BEGIN DAM IN CANYON

WITHDRAWABLE PUMPS—WORK UNDONE.

The works at Mangahao at present present a busy scene, there being over five hundred men employed. Some of the more important portions of the work are running three shifts six days a week. The weather has been so uniformly bad that the men are becoming to some extent amphibious, and on days when it is hardly fit for a dog to be out the motors hum and the crushers grind away At the dam in the Mangahao Stream a. great fight is goiug on against the forces of Nature. The dam has to be placed in a canyon, which, when the river is low, has twelve feet of water in it; and in the canyon floods rise as much as twenty feet'additional, and they are not slow at rising either. Coffer dams constructed of interlocked steel sheet piling hsrvo been built; two rows '' above and two rows below the site, and tho space between thes 8 double rows has been filled with concrete and other material in an endeavour to obtain a water-tight wall. A duplicate outfit of motor-Hriyeu 10-inch centrifugal pumps has been installed, suspended on inclined ways, so that they can be wound up fast enough to keep ahead of the risinir floods. b TOILSOME START AND PROMPT FINISH. The building of the coffer dams was quite an undertaking, one of the difficulties being the small amount of loose material in the canyon; in other words after the piling was driven there was not enough lateral support for it. It was braced from side to side with heavy timbers and guyed, to ring bolts let into the rock, with stout wire cables. Floods have bent the piling, broken the timbers and the wire ropes, and generally upset matters, but the dam-builders simply set their teeth nnd built it again. Finally the. pumps unwaiered the hole, and every 1 man available was put into the excavation, from which the spoil was hoisted and carried away with I ThY« ? f t, ramUnes- eleotric cranes, etc fJ« *ay W6ek lOck wa3 exposed and the first concrete was put in With in ten minutes of the completion of the work the rising river swept over the whole, and filled the excavation with water and shingle. Twice during the week the river subsided to a BU ffi c i en \ extent to enable pumping to be resumed, but not long enough for the hole to be clea?ed and any work' to be done. When the

excavation was finally unwatered on Tuesday, nothing was left of the work done but a few twisted steel bars which had been cemented into the rock to secure the first of the concrete.

BUILDERS BUILD ANEW. Still, the staff are not. discouraged. ■Ineae difficulties have to be met in all such works, and it is expected that before very long the coacreto will be up to such a level as will enable the dambuilders to laugh at all except the most stupendous floods. During October there were only eight fine days, and 10* inches of rain fell. September was a comparatively good month, with fourteen fine days and only U inchss of rain. It is alleged that a number of men who have been on the ■works from the early stages are already developing webbed feet.