AUCKLAND’S WATER

Sun (Auckland), Volume 1, Issue 12, 5 April 1927, Page 9

AUCKLAND’S WATER

THE TAUPO SCHEME A TEN-MILE TUNNEL engineering difficulties n ' ca ' evidence in support of the proposed Taupo and Waikato water supply schemes occupied the major portion of yesterday afternoon s sitting of the Water Commission, Messrs. W. A. Gray, G. L. Murray, and T. R. Gulliver, all of whom were cross-examined at some length regarding the practicabihty of the suggested proposals, affirming the necessity of obtaining an increased supply *or the city and surrounding districts. UNDER THE HARBOUR Questioned by Mr. A. H. Johnstone regarding his proposal to take water across to North Shore in mains laid upon the bed of the harbour. Mr. W. A. Gray considered that newspaper criticism of the scheme was exaggerated. Provision would be made to duplicate the main at a later date. An objection to answering questions regarding the Taupo scheme was raised by Mr. Gray. Witness stated that the report was merely a preliminary one, and in any case the scheme was only regarded as an ultimate source of supply. The chairman pointed out that the possibilities of Lake Taupo as a future scheme was one of the questions which they were asked to investigate.* ENGINEERING DIFFICULTIES Continuing. Mr. Gray said he was aware that the country through which the Taupo pipe-line would pass was affected by seismic disturbances, but pipe-lines at Whakatane, on the same earthquake line, which had been filled under pressure, had withstood earthquakes without any sign of subsequent leakage. In dealing with earthquakes he pointed out that the City Council had taken some risk in placing the Waitakere dam just above a 300 ft cliff. Reverting to the Waikato scheme, he did not think that that water would require to be chlorinated, although filtration would be necessary. In regard to the construction of a ten-mile tunnel, by which it was proposed to save 30 miles of pipe-line at an estimated cost of .£225,000, Mr. Gray stated that difficulties would certainly be encountered in the construction of a tunnel that length. If the scheme was proceeded with, it would be the longest tunnel in New Zealand. Mr. Johnstone read extracts from a Government report on the Waikato water, in which it stated a large number of micro-organisms existed. Mr. Gray: There are degrees of unfitness. The other day we read a report on two Waitakere samples. One was unfit for human consumption, and the other was five times as bad. Mr. Johnstone: But why go to the Waikato for dirty water when we can get it so close at hand? Messrs. G. T. Murray and T. R. Gulliver also gave evidence, disagreeing with the city engineer’s estimate of the quantity of water available from the Waitakere ranges. LAKE TAKAPUNA That the cost of eliminating contamination at Lake Takapuna was almost an insuperable obstacle was the opinion expressed to the Royal Commission this morning. Giving evidence upon the suitability of Lake Takapuna as a source of supply Mr. A. Slinger, engineer to the Takapuna Borough Council, said that it was obvious that a certain amount of water falling outside the catchment area found its way into the lake. To prevent, absolutely, contamination it would be necessary to forbid the erection of buildings or the grazing of stock over the whole area which contributed to the supply. That, of course, would be impracticable. lie considered it would be advisable in the interests of the borough to go to some source the quality of which was known. The annual consumption from the lake amounted to approximately 360 millions, and owing to the fact that the lake had fallen during the past years when rain was plentiful, it was apparent that in future years the lake would continue to decrease. Tie was of the opinion that the lake was fed to a certain extent by artesian springs, but as to the actual quantity he was not prepared to estimate. EFFECT ON PIPES A sample of a four-inch main which had been in service for 34 years was submitted by Mr. H. Griffiths, engineer to the Devonport Borough Council, showing the effect of incrustation from the Takapuna water. The witness pointed out that the main had been reduced from 4in. to 2 tin. He stated that the Health Department, who had examfried the pipes, had ascribed the cause to the presence of iron bacteria in the water. Mi*. F. E. Powell, engineer to the North Shore Water Board, gave it as his opinion that Lake Takapuna was fed almost solely from rainfall. He considered that it only the heavy rainfall experienced over the past few years, together with low evaporation that had maintained a sufficient supply. The consumption of water was still increasing and a proposal was outlined some years ago to supplement the supply with water from the Wairau Stream. If such was adopted it was intended to take the water only in time of flood when only a minimum amount of harmful bacteria would find its way in. and also chlorinate the water before entering the lake. (Proceeding.)