TECHNICAL DIFFICULTIES IN BIG SALVAGE PROBLEM

Press, Volume XCIV, Issue 28130, 20 November 1956, Page 14

TECHNICAL DIFFICULTIES IN BIG SALVAGE PROBLEM

THE BLOCKED CANAL

[Bv a Financial Times Reporter) (Reprinted by Arrangement)

London, November 7.—Once military operations in Egypt have been concluded. the authorities face what is likely to be one of the most important —and, possibly one of the most difficult —salvage operations of modern times —clearing the Suez Canal. According to current reports at least nine blockships have been sunk in the canal—four near the Port Said end two more near Ismaiha and Lake Timsah. and three at the Suez end. [More recent reports put the total obstructions at more than 20.] One of the blockships is believed to be a 3000-ton dredger belonging to the Suez Canal Company, and another is thought to be filled with concrete and explosives. In addition, the El Firdan bridge is reported destroyed. Units of the Navy available for clearing work include fully-equipped salvage vessels. The Navy is likely to be assisted by representatives of the Suez Canal Company who have had experience in the past of removing obstacles from the canal. Civilian Help? While nothing has yet been said officially, it is possible that experienced civilian salvage contractors may also be employed, in order to concentrate the maximum effort on a task in which speed is vital and the cost, although heavy, is of relative insignificance. The type, size and distribution of the blockships along the canal will dictate both the conduct of clearing operations and the time they will take.

Aerial reconnaissance can show where and how the blockships are situated, and give an idea of their size. The smaller the blockship, the easier the task of removing it is likely to be. One of the worst obstacles, believed to be a tank-landing ship, is lying broadside across the canal near Ismailia. blocking about three-quarters of the channel. The nature of the blockships, however—that is. whether they are filled with concrete explosives, scrap iron, or whether they have just been scuttled —can only be determined reliably by on-the-spot investigations by the salvage authorities, including underwater examination by divers or frogmen. Until such investigations have been made, it is impossible to say how long it will take to clear the canal, or even how it will be done. . The simpler type of blockship, a vessel that has been towed into position and scuttled —represents a relatively straightforward salvage problem. In

such cases, direct destruction by ex. plosive is one possibility, assuming that no high-explosives have been / left inside. Another is to break the vessel up on the spot, using underwater steel-cutting techniques. Yet another method would be te send divers down to patch the vessel and seal it up. It could then be refloated by pumping in compressed air to drive out the water, and then towed away. In some instances it may even be possible to drag the vessel out of the main channel before starting to cut it up. Experience in harbours and rivers in France and the Low Countries during the last war, however, showed that the most difficult type of blockchip to clear is that filled with concrete. high explosive, or scrap iron, or a mixture of all three. During the war some of these proved too heavy to move or were too difficult or dangerous to break up on the spot by means of explosives, and were dealt with by dredging deep pits into which the vessels rolled. New Channels Possible

This “last resort” method of clearance would be impracticable m the Suez canal. One alternative method would be to dredge channels round these obstacles, providing safe clear passages for canal traffic while the task of cutting the obstruction to pieces on the spot could proceed more leisurely. Even if this method was adopted, however, it would take time—-

probably several weeks—to dredge the alternative channels. There are other disadvantages, too. Jn some parts of the canal, where it has been cut through rock, it is difficult or even impossible to dredge alternative channels for ships. Furthermore, since some of the most difficult types of blockship to remove may be those in the middle sectors of the canal, it will be difficult to get the right type of heavy salvage equipment to the spots concerned. For this reason, it seems likely that clearing operations will have to begin at both ends of the canal simultaneously, progressing from blockship to blockship imtil the canal is completely free of obstacles. Other difficulties are posed by silting. and by the tidal conditions at the Suez end of the canal. Here, the tide changes every six hours, with ? rise and fall of some six feet. This could make the task of clearing the ships considerably more difficult.