WATER FOR AUCKLAND.

New Zealand Herald, Volume LXIV, Issue 19604, 5 April 1927, Page 11

WATER FOR AUCKLAND.

TAUPO-WAIKATO PROJECT. f THE WAITAKERE RAINFALL. CITY ENGINEER'S ESTIMATES. DIFFERENCES OF OPINION. -4 The Taupo and Waikato water supply projects were subjected to some criticism before the Auckland Water Supply Commission, which continued its sittings yesterday. Earthquakes, swamp, the proposed ten-mile tunnel,. and other matters were discussed. A counter-attack was made upon the pregmt Auckland supply. Mr. A. W. Blair presided, with Messrs. A. Dudley Dolson and A. J. Baker. Mr. A. H. Johnstone appeared for the Auckland City Council,- Mr. H. Kogerson for a number of suburban bodies favouring a provincial water board, Mr. F. E. Powell for the North Shore Boroughs Water Board, and Dr. H. Chesson for the Health Department. William Arthur Gray, civil engineer, who in conjunction with Mr. John Rogers had prepared reports upon a water supply from Lake Taupo, handed in copies of the reports and a mass of other documents relating to the matter. He stated that in the preliminary investigations possible supplies from the Waitakere Ranges, Mangatangl, and Maungatawhiri were considered, and it was decided to proceed with fuller investigation of the Taupo scheme only. Since the presentation of' the first report in March, 1925, lie had given much further consideration to the matter, and had confirmed his original conclusions. Witness 3aid he had also examined a report by Mr. W. E. Bush, city engineer, on the future of the present Auckland water supply. In his opinion, Mr. Bush had been over-liberal in his estimate of the future mainfall in the ranges. The estimate appeared to have been based to a large extent upon the records taken on the catchment area. These dated back to 1911 only. The fall in the past ten years in Auckland city had been greatly above the average for the 63 years from 1853 to 1916, and he beloved that periods as much.- below the average should be provided for. The witness also stated that Mr. Bush's estimate of the total quantity of supplies did not tally with his rainfall figures. Mr. Bush apparently had underestimated the loss by absorption and evaporation in dry seasons, also the amount of storage necessary to meet a run of several dry years. The Auckland storage, in relation to all the other factors—consumption, rainfall, and catchment area—was insufficient, judged by the standards of two typical supply schemes, Sheffield and Sydney. The valleys in the ranges were so steep that it was difficult to provide adequate storage. In f-ct,' dams built there were capable of furnishing only '■ seasonal, not annual, storage. Taupo For the Future. Regarding the proposals for obtaining supplies from the Mahgatangi and Maungatawhiri Streams, Mr. Gray said that there was a great lack of rainfall data, as no continuous record had been taken. Mr. Bush placed the minimum supply in the diiest years at 8,1)00,000 gallons a day. Witness placd it at half this figure. Gross-examined by Mr. Johnstone, witness said that he and Mr. Rogers' had given almost no consideration to the Mangatangi supply because they knew practically nothing about it. They knew a little about the Maungatawhiri supplv. They did not apply to the City Council for information about iCs system, nor did they pay special visits to the ranges. The data upon which their original report was based came from Mr. Bush's report of 1921. Later they perused the paper submitted by him last year tp the Society of Civil Engineers. The witness admitted that the Taupo scheme was premature at present. He was not in a position to discuss an intermediate supply from Afapuni, but he considered that the time was ripe for obtaining a supply from the Waikato River at Mercer. He was a wars that it would involve filtration and pumping, but he did not think chlorination vrould be needed. The Ten-Mile Tunnel. Mr. Gray held to the estimate of 125,000 people at 50 gallons a head daily | on which the initial schem# was based, i In answer* to a number of questions about j the tunnel ten miles long, estimated to cost £225,000, by which 30 miles of pipeline was to be avoided, the witness said that much of the country would be goft papa similar to that at Arapuni. "I quita admit that the tunnel is a ,'dark horse,' " he added, " but even if the cost were doubled it would add less than 10 per cent, to the cost of the whole scheme." Asked whether provision had been 'made for putting in piles under the pipeline where it traversed swamps, the witness said that he and Mr. Rogers had not made special provision «for this. They knew that the line would have to traverse areas of low-lying ground. Mr. Johnstone: But you know that there are miles of swamp. Do you intend to lay the pipes, on the roads f Mr. Gray said he would not express an opinion. The report was only a preliminary survey. A Main Under the Harbour. Asked about the proposal in the scheme to supply North Shore through a single line of ball-and-socket-jointed pipes, laid on the bed of the harbour, Mr. Gray said it was proposed ona main, carrylug a little im£jT§ than current requirements, and put down a second one later. There should be no trouble from tidepressure. He was quite aware that the engineer to the North Shore Boroughs Water Board clid not approve the idea. So far as this earthquake risk was concerned, Mr. Gray he had made no special inquiries, but he believed that the Public. Works) Department had done so before deciding-upon the Arapuni power scheme. The latter would be on the propose pipeline. So far as that was concerned, the City Council had taken a certain amount of risk by placing the Waitakere dam just above a 300 ft. cliff. .. Mr. Jbhnstorie: Is it not a fact that there was a series of earthquake shocks in 1922 near the site of your proposed intake, and is it not on a fault-line ? Mr. Gray said that the existence of high "bluffs near Western Bay, extending far below water level, did not suggest, that reallv bad earthquakes had occurred there. A pipeline at Whakatane, on tho same fault, had behaved well in the 1922 earthquakes. , Mr. Johnstone read some extracts from a Government report upon the water of the lower Waikato which, he said, became progressively more impure as it neared the sea. The analysis showed- it to con-' tain large numbers of diatoms and other micro-organisms, and was unfit for dnnKill^. Mr. Gray: There are degrees of unfitness. The other day we produced a sample that was not potable and another five times as bad. ' Mr Johnstone: Then what is the object of going to the Waikato for dirty water when you can get it nearer at Mr Grav: The reason for leaving the Wait akc res is that if there is a dry summer you will get no water at a-1. George T. Murray and Thomas R. V,, Gulliver, civil engineers, said that they did' npt agree with Mr Bush estimates of tiJVft; supplies obtainable iroro r-nges. "Sikte inquiry will be continued to-day. .