Nightmare ship salvage operation if Setu Samudram is aligned as a mid-ocean channel passage
By PA Ramakrishnan (July 2007), Ex-Superintendent Dry Dock and Naval Architect, Calcutta Port Trust
Suez and Panama Canals, are land-based canals. The Suez Canal Authorities had the advantage of making the alignment of the canal in one straight line because of the availability of land and absence of any hills. This resulted in the Suez Canal authorities making a canal with about 1000 feet of width, and massive embankment wall on either side with heavy duty Bollards. Canal authorities have also made roads motorable on either side for unloading heavy salvage gear at site in case of emergency for quick salvage, and this facility is not possible at Setu Samudram.
Ships move in convoys of 20 to 50 ships at a time, one behind the other from Mediterranean to the Arabian Sea and vice versa covering a distance of approximately 150 nautical miles. A vast lake named GREAT BITTAR LAKE somewhere at the middle of the passage enables the ships in one convoy to give way to the ships from the other convoy to pass each other in the opposite directions.
There are several storms in the Sinai desert of the Suez occasionally and tug assistance is provided to tow a ship, one at the forward end and one at the stem to prevent deviation of course and to avoid ships running aground in the shallow banks on either side. The following notes from the diary of the author will provide interesting details about the method of salvage adopted by the Suex Canal Authorities.
Extracts from the “unique salvage method” as seen from the magazine, Ship & Boat Builder, UK, June 55.
The diagram illustrates a salvage method recently used by the Suez Canal authorities to retrieve a grounded vessel in the canal. A heavy wire rope is led from the vessel right across the canal and secured to a bollard located on the other bank. Such bollards with holding power of up to 100 to 200 tons are buried in strong foundation every 200 feet on either side of the canal throughout its lengyth. The wire is then tightened with very little sag, tow wire from a tug stationed in the middle of the channel is of sufficient length for maneuverability.
Resulting Pull P from varying angles alpha on diagonal rope, one side exerting a pull on the bollard, and the other side on the ship, while tug providing a towrope pull of 50 tons. See how the 50 tons is magnified several times depending upon the angle alpha. (If angle alpha is 2 degrees, the result pull will be 720 tons).
The tighter the wire rope across the channel can be drawn, the nearer will be the actual pulls closer to the maximum figures shown in the table. (See figure). (Ship winch is used to tighten the tope and remove the slackness).
We shall now take a look at the Setu Samudram Project. Will the authorities be able to build retaining walls on either side of the bank to install heavy-duty bollards every 200 ft. as required for salvage operation in the Suez Canal?
This is very significant in view of the storms, which occur in the open sea frequently, especially during monsoons. Ships can deviate from the shipping channel and get entrenched firmly on the groun on either side of the canal stopping all navigation.
This note reinforces the sage advice of Sir A. Ramaswamy Mudaliar Committee Report of 1956 NOT to make a channel cutting through Rama Setu. The salvage facilities of the Suez Canal type can be provided economically and timely only if Setusamudram is a land-based canal and NOT a mid-ocean channel.