AUCKLAND WATER SUPPLY.

New Zealand Herald, Volume XII, Issue 4270, 21 July 1875, Page 3

AUCKLAND WATER SUPPLY.

The Corporation Waterworks, although there is not yet anything in the shape of buildings visible upon the ground, have so far advanced that an adequate notion of their extent and character may be obtained by a visit to the site. Through the kindness of Mr. Errington, the chief engineer, Mr. Goodall, the contractor's engineer, and Mr. Blewdcn, one of the sub-contractors, wo were yesterday to inspect tho progress actually made. Those who are at all acquainted with the locality would bo surprised to see the immense body of water that has been already collected into the permanent bed which has been prepared for it. The area of this reservoir is liftcen acres, and its capacity represents a water storage of from 15,000,000 to 20,000,000 gallons. The embankment which encloses it is seven feet vertical, with a face of twenty-one feet on the slant. It is composed of thoroughly puddled clay, is of great lirmness, ai.d so tenacious is the material that its durability is undoubted. Of course it is thoroughly waterproof, and the effect of this is, that all surface drainage is effectually excluded. Hence the supply will be, in the strictest sense, a supply of spring water. The springs, since the commencement of the works, have discovered themselves to be of greater value ; and if there had even been any doubt as to their permanent yield, that doubt has by-fuller observation been set at rest. But what is most assuring is the completeness of the precautions that have been taken, and the ample security they afford against .any contamination from

extraneous sources. The nature of the ground has permitted the inaiu body of the water to be conducted to its present bed, but in aid of the capacity of the natural reservoir some twenty thousand cubic yards of earth have been excavated. Of course every cubic yard of earth removed gives place for a cubic yard of water, and we were informed that 10,000 cubic yards are yet to be taken out. Now, as each cubic yard of water contains about 170 gallons, these excavitions represent an addition to the natural storage of the ground of something like 5,100,000 gallons. The water-course proper will be a uniform depth of six feet. Including the contents of the reservoirs which are being constructed at the comer of the Ponsonby Road and Kyber Pass Road, the total of the available supply will be 20,500,000 gallons.. We have already, on two occasions, described from the specifications of the engineer, the machinery and scientific aids by which the distribution of the supply is provided for. We are, on the present occasion, rather concerned with the actual state of the works. The reservoir at the corner of Ponsonby Road is 230 feet above high-water mark. This site is composed of a tenacious yellow clay. The embankments arc thoroughly puddled, and ononeside arescveral feet above the ground surface. They are of great strength, l>eing terraced outwardly. They are so solid that even at the present, after a considerable period of rainfall, there I is no inconvenience experienced in walking upon them, and the displacement of the surface is very slight when loads are drawn across them. The pillars upon which the roof is to rest are erected. They are built of brick, of various heights. This reservoir will hold upwards of 2,000,000 gallons. The reservoir at the top of the Kyber Pass Road is 300 feet above high-water mark, and will hold 1,500,000 gallons. The construction of this water storage is rather more elaborate than that at Ponsonby Road. The ground is composed of friable volcanic soil. It was therefore expedient to let in puddlebanks of clay some nine feet into the ground, and a yard and a-half wide. These puddled walls are made of the most adhesive clay that can be found and carted to the spot. These reservoirs will be completely covered in, and their bottoms and sides will be faced with concrete. The whole of the works illustrate in a remarkable manner the highly scientific character of the engineering calculations, of which they are the result. To the unpractised eye, they do not ia the present state offer a very imposing aspect; but when one begins to contemplate the contingencies against which provision has to be made, they afford a very practical chart of instruction. The pumping engines will be driven by engines 150-horse power (nominal). The water will be admitted from the main reservoir through a tunnel to the pumps. Men were engaged upon the approaches of this tunnel yesterday when we visited the site. Men were also busy in scooping out the solid rock for the foundations of the shaft. The piping will pierce the Archill brick ground, and be carried along the northern side of the Great North Road to Karangahape Koad, thence by Newton Road to Kyber Pass. The high and low pressure cylinders of both engines will be of the following dimensions :—High pressure cylinders, i!o' inches in diameter ; length of stroke, 5 feet. Low pressure cylinders, not less (when bored) than lj-inch metal. The beams (cast iron) will be 24 feet long, with depth at centre 40 inches. The whole scheme of the machinery is very elaborate. The main delivery pipes connected to air-vessel are to be of cast iron, IS inches diameter, and IJinch thick. The air-vessel will be 12 feet high ; internal diameter, 4 feet. The enginehouse is to be brick upon scoria foundation. As to the power of supply and distribution, these works will be capable of pumping 4,000,000 gallons of water in the 24 hours. If we rougldy estimate the population of Auckland at 20,000 souls, this will be a supply of 200 gallons per head per diem. Of course no such maximum will be necessary for years to come. But inasmuch as 50 gallons per head per diem is considered an ample allowance, we mention it to shew that the capacity of these works will be adequate to the supply of four times the present population. The contractors (Messrs. T. and S. Morrin) have already despatched a representative to England to purchase the necessary machinery. The contract time will have expired on the 21st of November, IS7G ; but as there will be a month's grace, it may be about the middle of December in that year before the works will be handed over to the Corporation by the contractors. The Christmas holidays intervening, we may expect a. fete day to open the new year 1877.