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Plain sailing

Harbour bed improvement - An ingenious ground improvement project is smoothing the way for next year's America's Cup regatta.Jon Young reports from Valencia in Spain.

With the world's most advanced racing yachts arriving in Valencia next year to compete for sailing's ultimate prize, the America's Cup, the port has become the focal point of the city. The various adaptations to the port in preparation for the race will cost E200M (£135M), but behind all this there is a larger, more impressive development.

Starting in 1991, improvements and extensions to the port have been the main focus for the head of the Valencia Port Authority, Marcelo Burgos. 'We expect the number of cargo containers to double to 4M containers a year by 2015 so we need to make space.' Cargo arrives at the port from every continent, either for transhipment or for transportation to Spanish cities.

The port authority believes that a strong local economy is needed to sustain the port but in return the port can bring long term economic benefits to the area.

Spain's economy is currently propped up by the construction industry: the port mirrors this with much of its cargo being aggregates.

Valencia Port has changed and grown constantly since its inception in 1483, when Antoni Joan built a wooden bridge on the beach and named it 'Pont de Fusta.' Contractor Geocisa is now in a joint venture with UK firm Pennine to increase the port area by 350,000m 2 in an attempt to accommodate some of the increase in demand expected over the next 10 years.

Floating on a barge somewhere on the east side of the port are four Englishmen, a handful of Spaniards and the occasional Portuguese, all in a race against time.

'Working on this job is like working on the Tower of Babel, ' says Geocisa contract manager, Francisco Torreblauca, who has to give instructions to all the workers in their own language.

Since work began in September this year the barge has been keeping afloat two 160t cranes. Hanging from each crane is the most exciting piece of machinery used on the project - the Pennine Aquacaster, an adaptation of Pennine's HD130 Vibrofl ot.

A ibroflot is essentially a giant poker that uses a combination of gravity and vibration to shake its way through the ground. There are two important differences between the Aquacaster and the standard Vibroflot that it is based on.

First is the hopper sat on top of the Vibroflot, containing, in this case, 12m 3 of crushed stone fitted with a delivery tube that takes it right to the nose of the Vibroflot. The second difference is the water jet that delivers a powerful blast from the nose of the poker to clear surrounding material.

Over much of the site ground conditions at the dredged depth are soft to firm silty clay overlying a very dense gravely sand. The self weight of the system drives the vibrating end of the Vibroflot down approximately 10m to the sand where high pressure jets of water then clear a 1m diameter cavity.

While the jets clear the cavity, the gate in the nose of the crushed rock delivery tube opens and the stone drops out to fill the cavity.

This gate prevents any of the material from the seabed getting up into the hopper. The hopper and Vibroflot are then slowly lifted out of the ground leaving behind the crushed stone pile.

Very little material is lost using this technique because the crushed rock is delivered directly to the nose of the Vibroflot.

Two piles can be sunk for each hopper load, which improves the efficiency of the system.

When the second pile has been poured the Aquacaster is lifted out of the water and brought alongside the barge where a travelling 15m 3 hopper, which is continuously replenished, reloads the Aquacaster's hopper.

To help the project meet its March 2006 deadline two Aquacasters are working side by side 24 hours a day six days a week, with two operating teams each working 12 hour shifts.

A tug boat, operated by a local skipper, pushes a small barge loaded with crushed rock and fuel out to the larger piling barge three times a day to keep the workers well stocked day and night.

All contractors working in a marine environment experience various difficulties, such as unpredictable fluctuations in the weather and the dangers posed by passing port traffic. But there is another problem specific to piling on the seabed for which Pennine has found a practical solution.

'Correctly locating the placement of the pile would be hard work. The murky waters mean poor visibility so to overcome this we've fitted each cab with a Global Positioning System (GPS), which allows the crane operator to precisely locate the stone pile, ' says Pennine managing director Arwel Williams.

'The aerial for the GPS is attached to the top of the crane directly above the centre of the Aquacaster.' Using GPS to locate the piles means the crane operators can work day and night without the quality of the work being affected. 'In fact it's easier at night because there's no reflection of the computer screens, ' says Torreblauca.

Working in a marine environment can offer some peculiar challenges, such as removing the fish stuck in the rotor blade of the pump for the high pressure water jets.

'We tried everything to get it turning but there was a whole fish lodged inside the pump, ' exclaims Torreblauca.

The Geocisa Pennine joint venture accounts for E4M (£2.7M) of the total E86M (£58M) allocated to the east side development. When complete the project will bring another 1,350m stretch of quay to the port.

A new harbour wall will be built on top of the stone pile and fill is being used to extend the existing loading and storage area out 250m to the new wall.

To tie in with the port development there are plans to upgrade the rail network to make it as fast and efficient as the new high speed passenger rail that has spread over the country.

'The infrastructure is being improved to link the port to major Spanish cities. Less than 10% of cargo leaves on trains, but with an improved rail service we hope to increase this. There are already depots in place in Madrid that can cope with the extra cargo so it seems logical to push in that direction, ' says Burgos.

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