A STORM off the Atlantic coast of Spain in February 1979 spelt the end for
the cargo vessel Fran莽ois Vieljeux. The French ship, on what should have
been a routine voyage between Dar es Salaam in Tanzania and the northern
European ports of Rotterdam and Hamburg, went to the bottom in 1250 metres of
water. It might well have lain there forgotten to this day, had it not been
carrying a cargo of copper bars and zinc slabs. At current prices, the
Fran莽ois Vieljeux鈥檚 cargo is worth in the region of 拢13
million鈥攙aluable booty for treasure hunters.
In April this year, a converted fishing boat, the Redeemer, headed out to the
wreck. It is now moored there, spending the summer salvaging some of the 6600
tonnes of copper and 700 tonnes of zinc that was aboard the French ship. The
28-metre Redeemer is owned by Deep Water Recovery and Exploration, a small
Scottish salvage company with headquarters in Fife. Deep Water Recovery is one
of only two treasure hunting firms whose business is to scour the ocean floor
for bulky cargoes valuable enough to cover the cost of raising them to surface.
The financial risks of deep water salvage are huge, but lured by the possible
rewards the rival teams are developing technologies that will allow them to lift
large quantities of cargo from wrecks at ever greater depths.
The first specialised deep-water recovery methods arrived in the 1920s, when
an Italian company started using a crewed observation chamber and a mechanical
grab. The firm鈥檚 biggest operation was the recovery of gold worth 拢22
million at today鈥檚 values from the Egypt, lying in 120 metres of water off the
north west coast of France. In the years after the Second World War, the British
company Risdon Beazley with its 1300-tonne vessel, the Droxford, scavenged the
globe for wartime wrecks. The company took almost everything of any value to be
found in less than 300 metres of water, says Moya Crawford, the managing
director of Deep Water Recovery. In 1978, after clearing all the wrecks within
its reach, Risdon Beazley closed down, a victim of its own success.
Advertisement
Now only the deep-water wrecks remain, and Deep Water Recovery and its sole
competitor, the Franco-British company Deepsea Worker, have made extraordinary
progress in salvaging them. Salvaging caches of precious metals is relatively
easy, and even small finds can be profitable. But today鈥檚 deep-sea salvage
companies are hoping to make money from cargoes of less valuable metals such as
copper, nickel and tin, which have to be retrieved in bulk. Until recently this
has only been possible in shallow water鈥攋ust five years ago the record
depth for cargo recovery was a modest 360 metres. But this summer will be the
fifth season that Deep Water Recovery has spent salvaging the Fran莽ois
Vieljeux鈥檚 cargo from more than a kilometre down. And in the past year, Deepsea
Worker has salvaged at least half a dozen wrecks in European waters, some of
them at similar depths.
Competitive strategies
Although the rival companies have similar goals, they have adopted wildly
different strategies. Moya Crawford鈥檚 husband and business partner, Alec
Crawford, fitted out the 116-tonne Redeemer for salvage work in 1984. The ship
is kept on station above the wreck by a set of four anchors attached to mooring
winches aboard the boat. 鈥淭he system is very precise and much cheaper than a
propulsive positioning system,鈥� says Moya Crawford.
The Fran莽ois Vieljeux鈥檚 wide hatches give easy access for the
Redeemer鈥檚 hydraulic grab, a giant six-fingered claw with a 2.6-metre span that
can lift up to 3.5 tonnes at a time. And because the wrecked ship鈥檚 loading
plans are available, the most valuable cargo can be loaded quickly, Alec
Crawford says. The grab is suspended on an umbilical cable over 1800 metres
long, with a breaking strength of 60 tonnes. Underwater lights and a low-light
video camera allow Crawford to see what is going on down below. The camera is
mounted in a pressure-resistant chamber, which in turn is housed inside a
protective case. This assembly is attached to the grab by flexible mountings to
minimise jarring when the grab slams into the ship.
At the depth of the Fran莽ois Vieljeux, the equipment must withstand
pressures of more than 100 atmospheres. For the solid steel sections of the grab
this is not a problem, but large moving parts such as the talons are made hollow
to minimise their weight and maximise manoeuvrability and strength. These hollow
components are drilled with holes that allow water into the cavity to equalise
the pressure.
This design is robust enough to work at even greater depths, says Moya
Crawford. But going deeper requires a longer umbilical cable鈥攁nd this is
where the big problems lie. The umbilical used at present consists of an inner
core carrying the power cable and coaxial data cable, surrounded by three
weight-bearing layers of steel wire. 鈥淵ou can鈥檛 just add another length to the
umbilical,鈥� says Crawford. One crucial factor, she explains, is the amount of
power that the cable can carry. This is limited by the voltage drop over the
length of the cable and the amount of heat that must be dissipated. The only way
to compensate for the losses is to increase the power. But this requires a
thicker, heavier power cable which would make the entire umbilical unfeasibly
heavy. In addition, the extra power would generate more heat than can be
dissipated easily.
To combat these problems, the cable is being completely redesigned. The next
generation of umbilical will have a weight-bearing inner core made from carbon
fibre, which is as strong as steel but much lighter. Weight saved on the core
will allow a thicker, heavier power cable to be used which, along with the data
wire, will be wrapped around the core. This design allows the extra heat to
dissipate directly into the water. The new cable, which is costing 拢41
000, should work down to 6000 metres, says Crawford, giving Deep Water Recovery
access to 95 per cent of the ocean floor. The firm hopes to test it for the
first time this September with a new boat that is now being built, financed out
of the profits from the Fran莽ois Vieljeux.
A key factor in the company鈥檚 success has been its ability to keep operating
costs down to around 拢16 000 per month. The Redeemer can sail with a crew
of four, and the salvage work itself can be run from the wheelhouse by just one
person.
Deepsea Worker, however, is run on an entirely different scale. Before each
operation, the company employs a surveying firm that deploys sonar and remotely
operated underwater vehicles to locate a wreck. In deep water this alone can
cost up to $250 000. During the salvage work, the company uses a
130-metre converted drilling ship equipped with powerful but fuel-hungry engines
to keep it positioned at sea. The vessel has a crew of 37 and a salvage team of
a further 23 people. Each day at sea costs $35 000.
Deepsea Worker鈥檚 grab is different too. It was developed in 1994 by the
French ocean research institute IFREMER, and was first used to recover a
17-tonne cache of coins from a wreck in 2600 metres of water off the coast of
Oman (This Week, 17 December 1994, p 10). Like the Crawfords鈥� grab it is
operated hydraulically, but instead of having claw-like pincers it is shaped
like a clamshell. The powerful jaws have a 200-tonne closing force that can
crush or rip open ships鈥� hulls, and can lift up to 10 tonnes, three times as
much as the Crawfords can manage.
It can also operate at greater depth. Instead of being suspended on an
umbilical cable, the grab is lowered on the end of rigid pipe that is assembled
at the surface from 10-metre lengths of iron tube. Attached to the outside of
this pipe are the power cables and data cables for underwater lights and four
video cameras.
But there are disadvantages to this design, too. Lowering the grab to a depth
of 3000 metres and then hoisting it up again takes about 24 hours for the round
trip. Such a slow and expensive process demands big returns just to cover costs.
But even with this limitation, Deepsea Worker has had some spectacular
successes since it began operations last year. In a single ship lying a
kilometre down in the Mediterranean off Gibraltar, the salvors found dozens of
kilograms of gold, hundreds of kilograms of silver and hundreds of tonnes of
tin. In the Atlantic off the coast of Spain they recovered 418 kilograms of gold
from a wreck lying in 200 metres of water, and 350 tonnes of tin from a ship off
the coast of Alicante in Spain. But with such high running costs, false leads
can be costly. The company wasted three weeks looking for the tonne of gold in
the First World War wreck of the Ancona, which went down off the coast of
Sicily. It also failed to find the Second World War wreck of the Laconia
believed to lie in 500 metres of water off the coast of southern Ireland.
Heavy losses
Philippe Poirir d鈥橝nge d鈥橭rsay, a director of the French shipping firm that
is part-financing the work, admits that the company has 鈥渕ade heavy losses so
far鈥�. He says the position should improve in September, when the company hopes
to start using a new grab capable of lifting greater loads from depths of up to
6000 metres.
Despite these technical advances, deep-water salvage remains a financially
risky business, from which profits can only flow while there are valuable wrecks
left to exploit. Just how many of these there are is open to debate. D鈥橭rsay
estimates there are about 50 worth going for; Moya Crawford says she is
interested in only 10. But this is not an industry where normal investment
criteria apply, according to Peter Edwards of the London-based Salvage
Association, a marine surveying organisation funded by insurers. He points to
other reasons for people wanting to get involved. 鈥淚t鈥檚 the excitement, like
treasure hunting,鈥� he says. 鈥淏ut if I won the lottery, I certainly wouldn鈥檛
invest in salvage.鈥�