Engineering Wonders of the World
Volume III

382 ENGINEERING WONDERS OF THE WORLD. of devising some scheme for supplying good water in an adequate volume and at reasonable prices. Orders to report on Government practicable schemes were is- takes Action. guec^ anj after several months of surveying and estimating Mr. C. G. O’Connor, M.Inst.C.E., laid before the Government the three best out of thirty-one alternative pro- posals. Of these three, the one to supply 5,000,000 gallons per day, through a steel pipe 30 inches in diameter, was selected as the basis of the final scheme. The supply reservoir would be formed by damming the Helena River in the Darling Range, at Mundaring, about 20 miles from Perth. The catchment area The Scheme. wag 569 s^uare mßes in ex_ tent ; and the authorities decided to provide sufficient storag© to meet the waste and use of two years in time of total drought. From the reservoir the water would be led by pipes to Kalgoorlie, over 350 miles away, passing through Coolgardie en route. Two great difficulties faced the engineers. The first was that th© reservoir had an elevation of but 340 feet above sea-level, whereas Kalgoorlie lay about 1,000 feet higher still; while in between were ranges of hills to be crossed, one of them rising to nearly 1,600 feet above th© sea. So that, instead of flowing by gravitation, as is th© case in all other large aqueducts, the water would have to be forced from point to point for the greater part of its journey against a total resistance allowing for frictional resistance—equivalent to a single lift of about 2,650 feet. In order to bring the pressures within practicable limits, it would be necessary to divide the pipe line into sections between the main storage reservoir and the highest point on the route ; and to provide at the western end of most of the sections a powerful pumping installation, draw- ing its supply from a stand pipe or a regulating tank. The second difficulty related to the question The Locking“ bar Pipe adopted. of the best kind of pipe. Cast-iron pipes were put out of court by the cost of sea and land carriage. It was neces- pipes sary that the pipes should be of steel, for lightness’ sake, and of such a type as to occupy a minimum space aboard ship. Tenders were invited from Australia, Europe, and America, and eventually the Mephan-Ferguson patent locking-bar pipe was adopted. Th© pip® consists of two steel plates, each of the full length of the pipe and bent to a semicircular form. The beaded edges of the plates are inserted in long bars having deep grooves on either side ; and the bars ar© closed cold over the beads by power- ful hydraulic presses. Th© pipes for the Coolgardie aqueduct were assembled in Western Australia out of plates imported from Germany and America and bars shipped from England. Every pipe, after being assembled, was sub- jected, in a special apparatus, to a hydraulic pressure of 400 lbs. to the square inch, and returned to the closing machine for re-pressing if it showed the least symptom of leakage. It is an interesting proof of the efficiency of the locking-bar system that only about fifty out of the 60,000 pipes required for the line failed to pass this test. The site of the containing dam for the storage reservoir being some miles from the nearest railway, a light line connect it with, that railway. August 1898 saw the comple- tion of this preliminary work. In April 1899 excavations for the foundations of the dam commenced. On being opened up the rock was found to be far less solid than trial pits had led the engineers to think it would be. A great fissure, running at right angles to the axis of the dam, was discovered , and, as the site could not be changed, the miners had to follow this fissure to sound rock, some 90 feet below the river bed. The foundations were formed of concrete to bed- was Duiiu The Helena Dam.