OPERATIONS TO BEGIN SOON FOR “DEEPER AVON.”

Star (Christchurch), Issue 18189, 23 June 1927, Page 6

OPERATIONS TO BEGIN SOON FOR “DEEPER AVON.”

MR STEWART STARTS BIG WORK NEXT WEEK

Some months ago an experiment, under the direction of Mr R. T. Stewart, Dunedin, was made in the Avon between the Colombo Street and Manchester Street bridges to show the possibilities of deepening the stream by lifting the silt on the river bed, and the experiments were so encouraging that the Christchurch Drainage Board decided to enter into a big scheme of carrying out similar tvork from as far up the stream as Fendalton Bridge and down to New Brighton. It is possible that the Lyttelton Harbour Board will continue the work to Sumner and on to Heathcote, so that small coastal Y-essels may be seen nearing Christchurch.

Mr Stewart and assistants have been busy for some time past fitting up the machine on the upper reaches of the Avon, and by the middle of next week it is hoped to be able to begin operations. Constructional operations on the craft have been impeded by the recent stormy weather, but the riversweeping plant is nearly in order. The structure on the river below the Fendalton Bridge has excited a great deal of attention since it has been in the stream. Over all it is forty-one feet in length, eleven feet in beam and has a draught of two feet. The hull, which is of steel, is twenty-one feet long and eleven feet wide, and the projections bow and stern make the length up to forty-one feet. The machinery is under a low deckhouse, built in sections so that it can be removed quickly when low bridges arc met with. Each pump to be used is able to deal with 18,000 gallons of w r ater an hour, and each pump will be operated by a 24 horse-power, fourcylinder Dodge engine. The water will be drawn from the stern through five-inch piping and delivered at the forward end through four-inch pipes, the jets being 18in in diameter.

In the language of laymen, the general scheme is that the water, after emerging from the jets, passes through a steel cylinder with a branch pipe extending abo\’e water level. Through this pipe air is brought into the cylinder and automatically wraps itself as a sleeve or ribbon around the jet, preventing the water from the jet coming into contact w’ith the water from the river. This air sleeve is carried down by the jet of water and forced into the material and mud on the bed of the ri\-er. What happens when the plant is in operation is that the material, with globules of air, becomes as a sponge, and is forced to the surface in violent ebullitions. Weeds will be forced away and the mud disturbed and carried downstream in solution. Any portion too heavy to be dissolved will be deposited back in the stream for further treatment. When the blanket of silt and material is removed from the bed the springs which are under the rWer will be liberated. with the result that the quantity of water in the Avon will be increased.

The machine which is being constructed will be controlled by the pressure of the water supplied to the jets, and can be deflected from one side of the ri\ r er to the other. It is expected that at least five chains a day will be cleared. At the end of a month the foreman of the board will take charge, and in the first month he will receive tuition as to the working of the plant.