salvage

salvage. From around the 14th century many Italian and other coastal cities already had sea laws in place that defined a split between the finder and the original owner in the value of salvaged goods brought into their harbours. In most cases this was dependent on whether the goods were recovered floating on the surface (see flotsam), or from the sea bottom (see lagan), and how close the shipwrecks were to the harbour. In the late 19th century salvage became the compensation paid by the owner of a ship or a cargo in respect of services rendered by persons, other than the ship's company, in preserving a ship or cargo from shipwreck or fire, a process in which tugs often played an important role. Lloyd's Form of Salvage Agreement (Lloyd's Open Form) was first adopted in 1892 on the basis of ‘no cure, no pay’, and it has been evolving ever since. In the UK salvage by an individual or a company is governed by the legal definition of wreck.

But the word salvage has other meanings, too, from the skilled techniques of firms employed to raise, or move, dangerous wrecks, to the activities of individuals who undertake diving expeditions to recover sunken treasure. Nowadays, sites are protected from the activities of the latter and marine archaeology plays a major role in preserving and interpreting what has been found. For example, the Mary Rose was a salvage operation but was undertaken by experts with conservation as the primary objective. However, marine archaeologists and salvage operators often use the same equipment, though their objectives are often different. Side-scan sonars are used to locate wrecks accurately and divers' salvage reports have been replaced by television surveys carried out by underwater vehicles.

From the second half of the 15th century onwards exploration by sea saw many European ships being lost around the world. Among the Caribbean islands in particular, seasonal hurricanes sank any number of Spanish treasure ships before they even reached the Atlantic Ocean for the voyage home. Salvage from such wrecks soon became a thriving business. Locals using free-diving techniques were pressed into service, not only by the Spanish themselves, but by many other nationalities who wanted to recover a fortune from under the sea.

In the late 17th century an American-born Englishman, William Phips, found sponsors for an expedition to investigate the wreck of the La Nuestra Señora de la Concepción off the island of Hispaniola. Sailing in a ship supplied by the king, he located her, against the odds, and his divers recovered a staggering 37 tons of treasure, worth at that time £207,600. Arriving back in England in June 1687, Phips received his one-sixteenth share and was knighted, while his main sponsor, the Duke of Albemarle, became a very rich man. In the years following Phips's success much of the coastline around Britain and the Americas, then owned by the British crown, was to be divided up and sold off to potential wreck hunters, with the crown taking a share of the profits. However, many investors went bankrupt, including the author of Robinson Crusoe, Daniel Defoe.

Early salvage methods usually involved the recovery of both goods and guns. Grapnels, attached by divers, ripped off the decks of sunken wrecks to allow the divers vertical access. The alternative, described in 16th-century editions of Vitruvius, a Roman architect from the 4th century ad, was to lift and move an entire sunken vessel. In a method used successfully in a Venetian lagoon, two sailing ships positioned themselves either side of the wreck linked together with wooden beams. Lifting ropes were run under its hull and the wreck gradually moved into shallower water, helped by successive incoming tides. From then on this was the general method used in raising a wreck, though each one presented, and presents, a different set of problems. Certainly, salvage work became much more efficient with the introduction in the 19th century of steam winches. Using well-developed rigging techniques, and the wire rope which was introduced towards the end of the century, these provided enough power for even wrecks to be rolled over.

Many ships posed a danger to shipping by sinking very close to port or, as the Vasa did, in the harbour itself. Stockholm already had wreck removal measures under way in the early 17th century, as did Sheerness dockyard in England. At Sheerness, gunpowder was employed to clear a channel of a shipwreck. It was sealed in barrels, lowered to the bottom and then ignited from the surface by means of a gunpowder fuse inside a long leather pipe. The same method was used later in the century, for clearing the River Tiber between the sea port of Ostia and Rome, and again for the removal of the wreck of the Royal George. As diving techniques improved, there began a golden age of stories of treasure recovered from wrecks. Typically, after the Alphonse XII sank off Grand Canary in 1885, divers descended 51 metres (160 ft) to smash their way through a number of decks and reach the strong room, recovering £90,000 of the £100,000 of gold being carried. In 1917 the liner Laurentic, a casualty of war, went down with £5,000,000 of bullion of which 99% was later recovered by salvage operators. When the ocean liner Egypt sank in much deeper water in 1922, an observation chamber directed surface-operated grabs which recovered three-quarters of the £1,045,000 in gold aboard.

Improvements in water pump and air compressor efficiency opened up many more possibilities for innovative methods by professional salvage companies. After the German High Seas Fleet scuttled itself in Scapa Flow in 1919, all but one of the wrecks was removed using access tubes with airlocks so that workers could enter the hulls below water level and work under pressure. Divers could also install patches over holes in a sunken hull, then attach air hoses which pumped air into the hull to restore enough buoyancy for it to be moved. Lifting caissons were often employed, as with the wreck of the US submarine Squalus, which sank off the east coast of the USA in 1939. Caissons were rigid structures that offered a fixed volume and a known lifting capability, but small wrecks or objects are sometimes raised using flexible lifting bags. However, great care is needed, as once enough air is added for them to lift the weight from the bottom, water pressure lessens and the air begins to expand. This creates more buoyancy, and the lift can get increasingly out of control.

Where a wreck cannot be moved or hoisted it is cut up instead. In the past, a chain was used to cut through parts of a hull which was worked back and forth using winches or cranes. However, there is now a more efficient flexible wire saw available, and this was used to remove a dangerous wreck in the English Channel in 2003. With the sunken 14,000-tonne Russian submarine Kursk, whose salvage began in 2001 from 100 metres (330 ft) of water, the damaged bow was first cut away. Divers then cut holes in the hull, wire ropes were attached, and the two parts lifted separately.

Peter Dick