DREDGING THE THAMES

Taranaki Daily News, Volume LV, Issue 305, 17 May 1913, Page 9

DREDGING THE THAMES

HUGE TEN-YEAR TASK. TO BRING SHIPS TO LONDON TOWN. London, March 21. in the next ten years about 00,000000 tons of day and sand will be taken out of the Thames between London "ridge and Southend. The old river, that was good enough for the Romans, for the battleships of Drake and Hawkins, and even for the liners of ten years ago, was becoming out of date. In the past there was no boat that could not come up the 1 liam.es at any time, but now there h re several that can come-up only at "liMi water, They had to wait for the tfde as it they were on a small provincial nver, and even then they cannot come lip as far as they would like, but have to stop some thirty miles from London Bridge, so that their passengers have a dreary train journey, and the cargo has to be brought the rest of the way by rail or lighter. J £IOO,OOO A YEAR TO KEEP UP. The Thames is still, of course, the busiest river in the world—every day 900 vessels go past Gravesend either outward or upward bound—but it has not ' kept pace with the growth of ships. The draught of liners has increased every I year, but the Thames is little deeper than in the Ho mm days. For thousands of years it served as a highway without a penny being spent on it. Not till 200 years ago was it systematically surveyed and then only a few hundreds of pounds were spent on maintaining the depth by confining the channel. Not till 1894 was it realised that the depth would not only have to be maintained but increased. Today the deepening plant is worth at least £500,000, and 500 officers and men are engaged on the dredgers, hoppers, and surveying steamers and launches. In wages alone the work of keeping, the river sufficiently deep costs about °£looo a week. The stream that has been so useful and cheap a servant for centuries is now to cost about £IOO,OOO a year to improve and keep up. TAKING OFF FOUR FEET FOR FORTY MILES. Right up to the Albert Dock the depth has to be made 30 feet at low water. i Now it averages about 20 feet, but in places it is considerably less, even 18 feet. That is to say, an average of four feet has to be cut off the bottom of the channel for a distance of nearly thirty miles. But this is not all. Beyond the Albert Dock the depth is to be made 20 feet as far as the Greenland Dock, and then lfi and 14 feet as far as London Bridge. So that practically four feet have to be taken off the bed of the whole forty miles of river from the mouth to London Bridge. THE •'HOPPERS." ) It is probably one of the biggest dredging work* that has ever been tackled. It is estimated that 115,000 tons will be raised every week for the next ten years. • Already six dredgers are working, and three of them are working day and night. Twenty-one steamers—for some mysterious reason called "hoppeiV—are needed to carry the clay and sand out to sea, where it is discharged. From the dredger now working just below London Bridge the hoppers have to ' steam 120 miles out and back. They are not allowed to discharge till they ' have reached a buoyed-out area known as Black Deep, about twenty miles out ' to sea, where the water is 70 feet deep. I ' Naturally, it is important that these mil- j ' lions of tons from the river-bed should be deposited only in a specified area, ' and careful precautions are taken'to see ; that nothing is deposited except at Black : Deep. Every hopper that leaves the ! river, whether by day or night, is reported to the Port of London Authority. ' and the watchers at the "Edinburgh" ' lightship near by. keep a record of every ] ; hopper that discharges there. ' ' A Daily' News and Leader represents- ' tive who was taken down the river by the dredging superintendent, by courtesy of the Port of London Authority, found the work in full swing. The five'bucket dredgers were all scooping up their thou- 1 ; sands of tons of dark grey clay, the still more wonderful suction dredger was ' sucking up its thousands of tons of sand, '■ the heavy laden hoppers were hurrying out to sea and back again, aiid the surveyors were taking soundings from their ' launches. '

A WONDERFUL DREDGER. No. 0 dredger, the host and newest of the bucket type, which cost £47,000, was working near Gravesend. It is a wonderful machine to watch. The superintendent speaks fondly of it as "a good tool." It is certainly a* powerful one. Behind every bucket as it cuts into the river bed there is a force made equivalent to HOOO h.p. by means of gearing, though the engines are only of 415 h.p.. and in one hour the machine can easily raise 1100 tons. Whatever a bucket 'touches has to co come up. One day a liner's anchor weighing three tons 'was brought up without a murmur from the machinery, and a short time ago a part of an oid dredger, weighing about live tons, suddenly appeared among the clay. Sunken boats, whether of iron, steel, or wood, are all broken up and brought to the surface. The dredger at London Bridge recently struck what was apparently a wooden barge that had become embedcd in the clay. Great pieces of wood came up in the buckets, only to be shot into the hopper alongside. HOW THEY WORK. To watch the buckets coining steadily up without a pause is not at first an entirely pleasant experience. Kvery moment one expects to see something besides clay and stones and scraps of wood and iron, something startling and dreadful, and it is a relief when nothing worse appears than repulsive slime, old pots and pans, a boot, a bowler hat. a dead cat, and scraps of clothes. Hour after hour the buckets climb steadily up to the top of the high platform", topple over to shoot their burden into the s.'ide leading to the hopper, and go down again i to the unknown ground whHi at bgh tide is some .10 feet below. The moment a hopper is f ully wdr-d it steams down the river out to sea, ami another immediately takes ;is i ace by the side of the dredger. Only tie I suction dredger, the Lord Desb.wgh, which cost £70.000, is independent of the hopper. When it is fully loaded it merely slips from its moorings under its own power and goes out to sea to discharge. ■** SUCKIKG SAND OFF THE OVERBED. It is a very ingenious but simple machine working on the same nrinciplc as the domestic vacuum cleaner. Instead of sucking dust oil' a carpet it sucks sand off the riverbed at the surprising rate of XVIO tons an hour. It's machinery is of :>(IOO h.p. Unluckily- it cannot quite do itself justice on the Thames. The sand is too muddy, and it cannot suck up more than 3 per cent. The '-est Is water, in coarser sand it can raise as much as 1.1 per cent. But it is only a question of time. The water runs out when the sand is settled, and in a few hours the enormous tanks are filled with '.othing but line dark sand. Off Southend, wnere the dredger is now stationed, it tonnages to raise TOO lons an hour, and a • •'<•; deal to the banks' of the estuary. Tt works day and night, pausing only to carry its load out to sea.

) LIFE ON A DREDGER. j Below deck it is very much like an j ordinary ship, with comfortably fitted cabins, saloon, bathroom, and kitchens, but on deck it is the very negation of a, ship. The first impression tlie visitor mis is tlr.-.t it is about to sink. Hundreds of tons of water seem to be rushing'about everywhere, and one ,'inds oneself not on a dry and reassuring deck hut on a narrow "platform Ictween two lakes of swirling water. To s'eep on Mich a vessel is not' only to have the river underneath but to liave a consider>able part of it above as well. Life on board is much the :<ame as life on a lightship, except that the captain i and crew have leave at the week-end and can go ashore. The only news of the outside world is brought by Hie hoppers which throw on board every morning letI ters and newspapers. The only breaks in the monotony are when the machinery breaks down, or when tin? lead of sand is carried out to sea, HANDICAPPED BY TUNNELS.

When the river has been deepened and the Albert Dock has been -xtended, vessels 800 feet in length will be able to come up to a point well within the cartage area of the metropolis. Whether the larger vessels of the future ".-ill |, R able to come further up is doubtful. The Thames is handicapped by its tunnels, which makes deepening below the proposed depths impossible. Some dny', perhaps, they will have to be closed or nede to burrow further below the river-bed. Luckily, however, the inflowing tide increases the depth of the river twice every day by 10 to 20 feet. Up to the Alliert Docks, then, vessels of the future with drafts of 25 feet and ;.p\v ; u'ds will be able to be safely navigated. Tt is but in keeping with the prominence of London that the water approach should be by far the deepest of all the ports of j the world. " I