CITY WATER SUPPLY.

Auckland Star, Volume LIX, Issue 230, 28 September 1928, Page 3

CITY WATER SUPPLY.

"IN A SOUND POSITION." EXPERT'S INVESTIGATIONS. FIRST DEVELOPMENT STAGE. — 'T consider that the City of Auckland is in a sound position with regard to its water supply. The existing storage dams are all at present overflowing, and, with the additional capacity provided by the raising of the Waitakere dam, there need be no apprehension of a shortage during the coming summer, while the completion of the Lpper Huia dam during the next year will provide a further storage sufficient to carry on for some vears to come."

The above is the opinion of Mr. H. H. Dare, M.E., M.1.C.E., of Australia, who has completed an investigation of the proposed extensions to the Auckland city water supply.

A comprehensive report by Mr. Dare was tabled at a meeting of the Aucklang City Council last evening. Replying to a number of specific questions, he urged that the Lower Nihotupu scheme should be undertaken as the first development following the completion of the Upper Huia works, from where plant and buildings could be transferred. Further storage would not be necessary until the end of 1041. This would allow ample time for the proper investigation of the Huia scheme, the preparation of designs, and putting the first section of the work in hand nine years from date. The expenditure of many thousands would be saved by that investigation. It would be premature to commence construction at the present time. The Hunua pipeline would be nearly forty miles long, and the preliminary work for transport of plant and material would take some time to construct. The construction of the works would taker longer than if all were concentrated in one place. The expenditure of the first section of the Hunua scheme would be between £1,500,000 and £2.000.000. Fire years would be a reasonable time to finish the work. At Hunua further information is required in regard to foundations and stream flows. At the lower site on the Mangatawhiri a dam 70ft high would store 1.130.000.000 gallons, and a dam of 90ft high 1,900,000.000 gallons. The catchment area at the lower site there was SOO acres larger than at the upper site. Consideration should be given to a dam higher than 70ft, and possiblv one of 90ft. Reasonable Estimates.

Proceeding. Mr. Dare said that the city engineer's estimates for the lower X iliotupu scheme were reasonable. In connection with the Hunua scheme there was not sufficient data available for a reliable estimate. An aerial survey photo would be useful, but he was doubtful whether it would sufficiently determine the levels of the ground service. A line survey should precede the calling of tenders for pipes, and tunnels could be constructed during the laying of the. 'pipeline. Investigations for the dam and pipeline c-ould proceed simultaneously. He considered that work at Xihotupu should commence about the beginning of 1930, and that in the meantime the plans should be completed. He did not think that the appointment of a special water engineer in charge of construction was necessarv.

Proceeding, Mr. Dare suggested that before proceeding -with the Hunua scheme the supply of water from the lower Huia should be further considered, and that the measurement of discharge streams on catchments should be developed, with the use of current meters combind with automatic stream level recorders.

Mr. Dare referred to the fact that the Auckland Water Commission adopted a figure of 60 gallons per head per day, in estimating the future requirements of the Auckland urban area, also an estimate that by 1967 the population in and around Auckland city should be approximately 575,000. He agreed with the basis of 60 gallons per head, but thinks that with strict supervision the average could be kept below 60 gallons. After referring to the figures supplied by the Water Commission in regard to storage quantities and catchment area, Jlr. Dare said that it is assumed that were the North Shore boroughs supplied by the city, Lake Papuke would be kept as reserve storage. His report was based on figures supplied, which gave the following particulars of storages and yields (the latter two in millions of gallons):—

Catch- Storage Yield ment Acres. Waitakere ...... 2100 45. Xihotupu ........ 2374 fiOO SJ Hnia 2040 .">OO 4 J Lower Nihotupu .. 900 ft Hunua .......... 10,200 3200 23 Slender Data. "It is on the above figures that my report is based," states Mr. Dare, "but I would point out that the data in regard to the run-off from Hunua catchments is very slender, and further investigations may lead to modifications. At Manga tang!, Hunua, no contour survey had been made of the storage, and at Mangatawhiri, where shafts had been sunk in search of a foundation, no rock had yet been struck. In consequence of that, and the fact also that surveys will not be made of tunnel sections, conduits, pipelines or filters, I am not in a position to express a definite opinion regarding the city engineers tentative estimates of £2,700,000 and £ 1.600.000 for the scheme.

In reply to Mr. J. A. C. Allura, Mr. Dare said he considered the Hunua scheme sound. The catchment area was satisfactory, and the quality of the water of a high standard. Later on the scheme should be developed by the City Council. Valuable information had already been obtained, but not sufficient to justify the work being put in hand yet. '"Are you of opinion it is better for the council to go on with the Hunua scheme than go for the W aikato River scheme?" asked Mr. Allum.

Mr. Dare said the investigation of the aikato scheme had not been referred to him by the council. He had read the report of the Commission, however, and he had come to the conclusion that there were strong reasons why the Hunua scheme should be adopted in preference to the Waikato. The Hunua source was unpolluted. This could not be said for the Waikato, where considerable settlement existed. In addition there was sediment in the river, and the water might have to be treated. For those reasons Hunua was preferable. The cost of the supply from the Waikato would be twopence per thousand gallons more than the Hunua cost. That was an added reason for choosing Hunua. He had not seen better water than the council was supplying. He had seen Arapuni, but not »n the Waikato River. The report was received and referred to a joint committee.