CITY'S WATER SUPPLY.

New Zealand Herald, Volume LXIV, Issue 19805, 28 November 1927, Page 10

CITY'S WATER SUPPLY.

HUIA VALLEY SCHEME. SATISFACTORY PROGRESS. PIERCING OF LONG TUNNEL. THE WORK OF CONCRETING. \ Tunnelling and pipe-laying operations on the route by which water from tho Huia Valley will bo brought for filtration at Titirangi before being distributed to city households are proceeding satisfactorily. It is hoped to complete tho laying of pipes, with the exception of the connections with tunnels, during the summer, and to have the whole of the system in working order by next November. An important development last week was tho piercing of tho tunnel through the main ridge dividing the Huia and Nihotupu Valleys. This tunnel is 4000 ft, long, and, when cleared out, will have an internal cross-section of 18 squaro feet. It is proposed to lino it with concrete to enable it to carry water without the laying of pipes through it. Water will bo conveyed from tho dam, for which the site is uow being prepared, to the tunnel by a steel pressure main, 21in. in diameter and 13,000 ft. in length. The grado of the tunnel is one in'3soo, which works out at a fall of about 14in., and the connection has been made to within a fraction of an inch. From the Nihotupu side of the tunnel a 27in. steel syphon, two and a-half miles long; will carry the water across the Nihotupu Valley to Macky's Rest, there giving place to a covered reinforced concrete conduit, two miles in length. The conduit will carry the water on tho final portion of its journey to the new filtration plant to be erected at Titirangi in close proximity to tho present plant. Tenders for the erection of this plant, the last of three planned by the City Council, will be invited in January.

There are five tunnels on the route between the big tunnel recently pierced and Macky's Rest. Two of these, one a quarter of a mile long and the other 200 ft., have already been concreted and lined, while good progress has been made with a third, which is over half a mile long. To facilitate work on this tunnel an adit was put down, thus enabling driving to proceed on four faces. The workmen have holed through the section on tho Titirangi side, and concreting will shortly bo started. The work on the remaining two tunnels is also well advanced. With tho completion of the schemes in hand, the total daily supply of water to the city will be 23,500,000 gallons, obtained from the following sources:—Waitakere, 4,500,000; Nihotupu, 5,500,000; Huia gravitation ,4,500,000; Nihotupu pumping 6,000,000; and Huia pumping, 8,000,000. At 50 gallons a head a day, this would suffice for the needs of a population of 560,000. As an index to the city's present requirements, a record was created this month, when on one day 10,000,000 gallons were drawn through the mains.