MT. VICTORIA TUNNEL

Dominion, Volume 23, Issue 55, 28 November 1929, Page 13

MT. VICTORIA TUNNEL

SYSTEM OF VENTILATION WILL ARTIFICIAL AIDS BE NECESSARY? With a tunnel over 2000 feet, long and wide enough to allow tram and motor traffic to pass through together, ventilation becomes a very important factor. In the construction of the new Mt. Victoria tunnel two big ventilation shafts are to be sunk. In the ease of the existing tramways tunnel through to Hataitai ir w(ts not necessary to arrange any means of ventilation other than what is provided by the tunnel itself. But with the piercing of a tunnel twice that breadth, which is to be used by motor traffic as well as the city tramways; some special methods of ventilation become necessary, as on a calm still day, with perhaps twenty or thirty cars and lorries in the tunnel, it Is just possible the air might become to heavily charged with carbonmonoxide gas for public safety Two ventilating shafts, each about 128 feet in depth, are being sunk from the hill slopes—one about a third of the way through from the Patterson Street portal and the other about a third of the way in from the Kilbirnie end. Each shaft will be Oft. squarea foot of lining and an eight-foot shaft. Will They Suffice? The problem that faces the Corporation at present is whether these two shafts will, by their natural draught, be able to carry off such fumes as the motor traffic using the tunnel is likely to emit. With the development of Wellington East (on the other side of Mt Victoria), which is bound to come with the piercing of this tunnel, the motor traffic of the future—say, tea years hence —is likely to be fairly continuous, and increasingly heavy, but for a start.it may not be very thick—' perhaps not heavy enough to justify the installation of costly aids ensuring forced ventilation. ' Provision is made in the plans of the tunnel for a inlet air duct (to run through the tunnel under- the elevated sidewalk), and it may be that when air is pumped into the tunnel through that duct, the added pressure of the loj-ced air in combination with the natural suetion of the shafts will be ample to ensure a liberal supply of fresh air for all using the tunnel. It is likely that any provision for forced ventilation will be progressive, and that measures will be taken to ensure the safety of the public in the tunnel as they are found necessary. Is Forced Ventilation Necessary? There are those who hold that the introduction of motor traffic into a confined space such as a tunnel demands forced ventilation, and they quote instances where people have been overcome by car-bon-monoxide fumes even in their own garages. They aver that in hot, still weather there is not likely to be much natural suction from the shafts, as the air of the tunnel will be cooler than outside, and on such occasions forced ventilation will be essential. . There is no provision in the existing contract for the supply of anything ,in the way of artificial or forced ventilation —all the Hansford and Mills Construction Company have to do is to sink and line the two shafts. It will be for the City Corporation sooner or later to decide on expert advice whether electric fans are to figure as part of the ventilating equipment of the new e tunnel.