PIPE SCHEME

Hokitika Guardian, 6 September 1939, Page 8

PIPE SCHEME

£IOO,OOO JOB IN ASHBURTON. Excelled in size in the world only by the siphons in the 335-mile aqueduct now being built to bring water from the Colorado river to Los Angeles, “precast” concrete pipes, 12 feet in diameter, are to be used to circumvent about one- mile and a-lialf of sliding country at Gawlor Downs, on Surrey Hills, in the Ashburton County. After a section of race was opened up on the hill, j, large slip endangered the scheme. About £IOO,OOO is involved in' the adopted scheme for conveying water for a distance of 8800 feet, operating under a maximum head of 125 feet.

The use of “precast” pipes, in preference to casting in situ, was derided by the engineers at a conference at Wellington last week, the District Public Works Engineer (Mr F. Laugbeini and the Irrigation Engineer (Mr T. G. Beck) being present. Work is to be begun without delay on the building of the second largest “precast” concrete pipe line in tin* world. With an inside diameter of 12 feet, the.pipes will have a wall the thickness of 10 inches. The units will have a length of 12 feet and weigh 27 tons. One of the features of the discussion by the engineers was. the necessity for very small tolerance The finest of workmanship willwhe demanded, for it is necessary that the diameter shall not vary more than onetenth of an inch.

Although the pipes will bo of unprecedented size for New Zealand —they will carry three-quarters of the normal winter flow of the Rangitata river—no difficulty in their construction is expected. The engineers have, the American experience of building 42 ton sections, with 12 ft. 8 in. diameter and 13-inch wall thickness to guide them. The fabrication and laying of the pipes are not exneeted to delay the completion of the main irrigation race from the Rangitata to the Raknia river, scheduled'/for September, 1940.