WATER FOR SHORE

Auckland Star, Volume LXXII, Issue 137, 12 June 1941, Page 8

WATER FOR SHORE

FIRST PIPES ARRIVE

SERVICE IN NOVEMBER

Sufficient for three-quarters of a mile, the first shipment of pipes for the pipeline that will connect the North Shore with the Auckland city water supply, has been delivered on the route. A further shipment is expected almost immediately, and the entire shipment should be on the job within four months.

Some of the pipes are being made in Australia, but the balance are being fabricated in the Dominion. Certain essential equipment, such as valves, has been ordered in England, but this will not hold up the start of the actual work. Provided deliveries are up to schedule, the water supply will be available by the end of November.

The most difficult section of the line will be through the bush between the Waitakere filters and Swanson, stated the city waterworks engineer, Mr. A. D. Mead, to-day. This work, involving the construction of a track and the building of piers over gullies, was already in hand. The remainder of the route would be on roads or through easy country.

The total length of the pipeline to a site at Birkenhead, where a reservoir is to be erected, will be 131 miles. Thereafter there will be about five miles of main to be laid on the North Shore to service the various boroughs. The pipes will vary from 15in to 18in.

The line will cross the harbour at a point between Kauri Point and Beachheven wharf. While the section of harbour to be traversed will be three-quarters of a mile, the actual tidal channel at this point is less than a quarter of a mile wide.

The mudflats adjoining the channel are of firm material, and at low tides they will be trenched and the pipes covered. Admiralty charts show the depth of the water in the channel at 30ft at low water, but fresh soundings are to be taken. The pipes for this section will be jointed together in one line on the mudflats, and the ends sealed. Filled with air they will then be floated out at high tide.

As the tide drops one end will be unsealed and jointed to the portion in the mudflat, leaving the other free. By gradually introducing water this free end will be slowly sunk to the sea bed, then joined up with the terminal on the other side. While the reservoir at Birkenhead is not essential to ensure a supply of water to the North Shore, it is being erected as a safeguard in the event of minor repairs and leaking joints. It will hold a day's supply of 1,000,000 gallons. The size of the mains is stated to be sufficient to give a 50 per cent margin of safety that is, it can supply a demand half as large again as the present. Reference has been made to the capacity of Auckland's dams and reservoirs to supply both the city and the North Shore during a dry period. The total storing capacity is 1,569,000,000 gallons, and it is interesting to note that at the end of the driest portion of last summer, one of the driest for many years, the dams were still two-thirds full (See picture on page 5.)