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The final countdown

Controlled Demolition carried out the first blowdown in Portugal, unaware it was to be the last job before the company went into receivership. Joanna Booth witnessed the collapse

THE TROIA peninsula points north-west like a hopeful thumbs-up, gesturing towards the Portuguese capital Lisbon, an hour's drive north.

Though it boasts one of the f inest golf-cou rses in Europe and its sandy beaches are still popular with locals from the surrounding area, many of the facilit ies on the 20 km-long st r ip of land were built in the '70s and are now past their best.

Portuguese developer Sonae has bought most of the land on the peninsula and is set to begin a £204 million project to transform the area into a tourist venue ? the papers are hailing Troia as Portugal's Marbella. Works on the resort, which will comprise several golf courses, a casino and a marina, will begin in November and continue for seven years.

But before work to build the new hotels can begin the old ones currently in the way must be demolished.

Previously, buildings in Portugal have always been taken down by traditional methods, but Sonae chose the glamorous route, believing that hosting the first blowdown in the country's history would put Troia on the map, and on everybody's lips.

The strategy clearly worked. On an autumn morning on a small car ferry from Setubal, Francisco, a 24-year-old from Lisbon, is telling how he is visiting friends in Troia specifically to get front row seats for the occasion. Most visitors have been discou raged f rom com ing to the island for the event. The ferry stops running at midnight the day before, stranding two bewildered American students who came across to watch kite surfers making the most of the strong winds.

By the blowdown day, the majority of the demolition is complete, with nearly all the low-rise buildings torn down. A long-reach excavator operated by local firm Fozterra was working late into the previous night, tidying the rubble of a former supermarket complex.

The two buildings earmarked for explosive demolit ion are hotels of 18 and 16 storeys. Only one was finished when the Portuguese contractor went bust and the other remained an unused concrete shell.

For the Controlled Demolition team, the blowdown is the culm inat ion of n ine weeks of work on site and seven years of waiting. The project was first discussed in 1998, but it was not until this year that the developer decided it was ready to go ahead.

The structures are soft-stripped and then the nonload bearing walls on certain floors selected to take explosive charges are removed. Holes are drilled into suppor t ing columns, packed with explosive charges and sealed off with gypsum-based cement.

St r ict calculat ions are made to ensu re that the building falls exactly in the way it is intended. The shape and composition of columns are tested and core samples taken. Cont rolled Demolit ion's in-house structural engineer, Rob Clarke, looks at the plans, check ing both that the intended paths of d r illing will not dangerously weaken the structure too early, and that the explosive charges will take out enough columns in the correct places to let gravity do the rest.

The first two f loors are heavily charged and then three others at regular intervals further up each hotel, with the last charges set only a couple of f loors from the top. 'The non-load bearing walls are left in on the f loors which aren't blown, ' Mr Clarke explains.

'Their weight ensures that the building collapses properly, especially near the roof where there is only the weight of a couple of f loors to break it up.' Project manager Dave Henshaw and his team of four workers have been out in Troia for over two months, reducing the hotels to concrete shells, drilling the blast holes and packing them with explosive charges. For most of the audience the blowdown is a momentary excitement, but for the Controlled team it is the culmination of weeks of hard graft.

Small Brokks ? remote controlled breakers ? have proven perfect for knocking openings, their tracks making the machines easily manoeuvrable up the hotels' narrow staircases. Controlled has reduced its use of hand-held drills by bringing in a robotic drilling machine, which exposes workers to much lower levels of harmful vibration.

Each hole is packed with leng ths of detonat ing cord ? plastic tubing packed with an explosive powder called pentaerythritol tetranitrate. This is the form of explosive most commonly used in tak ing down buildings. Sticks of gelignite are still sometimes necessary to take out particularly thick columns or to kick out steel legs from a structure, but for the most part detonating cord produces better results.

'The idea isn't to blow it sky-h igh, explains Mick Williams, Controlled Demolition explosives division manager. 'A stick of gelignite packs a powerful punch but it is in one small location. Det cord spreads the explosion over a greater area. We can take out the entire length of a wall with one line of cord.' Different weightings are available, from 10 to 100 grammes. The weight refers to the amount of explosives per metre of cord. Cord is also beneficial because it contains the explosive in a plastic coating.

If n it rate-based explosives come into contact with the skin the user can suffer from what the explosives team call 'geli-head'. The r ise in blood pressu re caused by the nitrate results in a severe headache.

Along with the base charge, the fuse is put into the hole before it is sealed with gypsum-based cement.

Each fuse contains a delay element which allows the team to control to hundredths of a second when each charge blows. This makes it possible to topple buildings in one direction by blowing the charges on one side of a building slightly before the other.

One of the hotels is within 500 m of another tower scheduled to remain and is being toppled in the opposite direction. To prevent debris flying great distances from the blast site, geotextile sheeting is wrapped round each charged wall.

'It's a woven nylon fabric which is very strong in tension, ' says Dick Green, senior explosives engineer.

In the few days before the blowdown all charges on the same f loor are connected by qualified explosives engineers. Brightly coloured shock tubes a few millimetres thick run between fuses and connectors, the small amount of explosive powder cased in plastic transmitting charge at 2,000 m/sec.

The entire job is using over 1,000 connectors, all of which will blow within a 50 millisecond window.

The blowdown is scheduled for 4 pm. Shortly after noon the Portuguese prime minister, Jose Socrates, is helicoptered on to the peninsula, taken for lunch at the golf club and then instated on a balcony to watch the show.

High winds in the night have loosened some of the protective sheeting and this is re-lashed to the building. Mr Williams, Mr Green and Mr Henshall work as a team, checking every single connection in the building. Every shock tube is neatly tied down, the complicated mesh tidied into a well-ordered chain so that the engineers can easily see that each connection is correctly placed. Moving from the top down, they connect each f loor together too, until all that remains to link up is the final connection to the detonator.

This takes place only an hour before the blast.

The team is used to a cer tain amount of excitement surrounding its work ? there have been streakers at a job in Edinburgh earlier this year and there are sometimes tears from local residents when they see a former home hit the dust. But the hoo-ha on Troia tops the bill. Security for the prime minister is sky-high. As well as 500 police officers on foot, horseback and in boats zipping round the shores, armed snipers crouch at the top of the surrounding buildings. Television cameras are everywhere, streaming live to the whole of the country for hours before the event. Reporters struggle as the high winds play havoc with their hairstyles and huge speakers boom out a Mozart horn concerto at deafening volume across the peninsula.

The music cuts out to allow the countdown to begin. The cameras may be focused on the plunger, nestling under the Prime Minister's hand, but those in the know are not fooled. A small cluster of men in hard hats a hundred metres back from the fenced-off exclusion zone are the ones to watch. Cont rolled's explosive engineers are the ones who really trigger the explosion.

The boom is predictably deafening, and the ground shakes. The first tower has partially crumpled when the second goes, toppling slightly away from the remaining building. Both fall in on themselves perfectly. It is a textbook demolit ion.

It's not only the ground that moves. The explosion causes a change in air pressure which feels like a strange gust of wind, capable of shattering nearby windows.

Monitoring vibrations both on the ground and taking the air over-pressure are Protec, a two-man team from the USA. Brent Blanchard and Earl Gardner travel all over the world monitoring demolition jobs for many different companies and filming each blowdown.

Along with the explosives team they are the first on the scene once the dust ? and there are two huge clouds of the stuff ? clears. The team checks that the blowdown looks as successful close up as it did from a distance, and the job is over.

The evening after a blowdown is a time for celebration, and this one is no exception. The high spirits are tempered though, by the escalation of rumours that the company is in financial difficulties.

The whispers of trouble had reached Portugal a week before the blast but, though worried, the team was planning the next job in Glasgow.

Mr Williams and Mr Henshaw have both worked in demolition for over 20 years, and survived a previous firm's collapse. They feel sure that their expertise will find a home.

The team's faith in the value of its capabilities proves well founded. Newly bought-out, the management team at the helm of Cont rolled is now planning to focus on the explosives side of the business.