FIRST PART READY

Ashburton Guardian, Volume 61, Issue 251, 5 August 1941, Page 7

FIRST PART READY

HUGE SIPHON AT SURREY HILLS SECOND SECTION UNDEft WAY. The immensity of the task of laying the huge siphon along the Surrey Hills section of the main diversion race on the County irrigation system is shown by the fact that already the Public Works Department has put down 8000 tens of concrete pipes with a diameter of 12 feet. The first portion of the siphon is complete, and about 400 yards of the second section has been put down. At the angle made by the two sections one of the two huge anchor blocks, consisting of many hundred tons .of concrete, will he built. At this point, probably, will also be constructed one of the entrances to the pipeline which will enable motor-lor-ries and other equipment, to be taken inside for the cleaning, and maintenance of the huge concrete tunnel. So far 280 of the 732 pipes in the compete siphon have been laid, and 18 or 19 more are being added each week. Each weighs 28 tons, so that the total weight of piping now laid at Surrey Hills is 7840 tons.

In addition, 18 of the smaller pipes, 11 feet in internal diameter, and each weighing 20 tons, have been built for the siphons which at several .points will carry the diversion race underneath rivers and streams. There will be seven such river crossings, and the only one which has not. yet been started is that at the North Ashlmrton River. Apart from these there will be several crossings of creeks and washes which are usually dry. The largest of the river siphons will be that beneath the south branch of the Ashburton River. Here will be built one of the most interesting structures on the project—a combined siphon, spillway and intake. At this point the water in the diversion race will be “boosted” when necessary by taking in part of the flow of the south branch.

A sloping weir behind the pipes of the siphon—which will be buried bfeneath the bed of the stream—to direct the flow of the river across to one side, is provided for in the scheipe. Part of the flow will be trapped and led through a series of control “chambers to the diversion race. The level of the water in the race will automatically control the amount taken in at this point. The intake regulator itself will be a huge structure of some 700 tons of reinforced concrete. The line of the siphon across the river-bed has been excavated for about half its length, and a start has been made with the concreting of the foundations. Half of the .pipes required are on the. site. Considerably more than 80 per cent, of the total excavation required for the main, diversion race has been completed. Up to .the end of June the proportion completed was 81.03 per cent-., and this represented the removal of 3,421,948 cubic yards of spoil. Good progress is also being made by the contractor on the construction of the power-house at Highbank which will use water from the diversion race for the generation of electric power The foundations were completed some time ago, and the superstructure is under way. Two of the cylinder foundations for the transmission towers across the Rakaia River have been placed, and two more have been begun.